This article will mainly explain things in terms of differences, so if you haven't already, go read the original Pocket WiFi article, and then come back here.

So what is the same, and what is different?

The main selling point is the new higher download speed, (42Mbit as opposed to 21Mbit in the GP01), however, there are many other small differences as well.

First, and most obviously, the Style and Color.  

The GP02 it considerably more hefty than the previous models, and black in color on both the front and back.  The back case still comes apart to change the battery and SIM card, but the SD-card is replaces in a similar fashion now.  Instead of "peeling off" as with the previous generation, it slides off like a typical cell phone now.  The front of the device is now a single sheet of plastic, so when the display is off, its not obvious that it even has a one at all.  It definitely looks a bit cooler than the previous generations, and the build quality is more solid and the unit is a bit more hefty (37% heavier than the previous models).  The buttons on the side have a more sturdy feel as well.  The entire thing is 57% larger, and so cases and other accessories for the previous models (Including the cradle) will likely not work so well with the GP02.  Despite being significantly larger and heavier on a percentage basis, the whole thing is still smaller than your average smart phone and continues to earn its name by fitting in your pocket quite easily.

Whereas the D25HW and GP01 both used the same battery, the GP02 uses a new, thicker battery.  The rated run-time for the 3.7v 2200mah battery is 4.5 hours, but the stand-by time is much longer. (The old battery was 1500mah) The charging socket is Micro-USB, the same as the GP01.  Although a larger battery is good news, the fact is that the run-time has only increased slightly with the larger battery, so the GP02 is definitely more juice hungry.  In fact, if you do the math, it uses about 30% more juice per hour than the previous models.  This makes sense, since it maintains active data connections to multiple cell phone towers in order to increase its download rate - the increased speed doesn't come without a price.  Charging takes quite a while (4 hours), even with the dedicated charger.  

The saddest thing is that any extended battery packs you may have purchased for the D25HW/GP01 have to go the way of the Dodo Bird when upgrading to the GP02.   Even if new battery packs come out, they won't last as long as they would on the previous models, due to the more power-hungry nature of the GP02.  For example, the 3rd party 5400mah battery packs for the GP01 should theoretically last around 14 hours, but even if they worked on the GP02, they would only last around 11 hours.   On the up side, in a pinch, you can use an external smart-phone battery pack for emergency power.

The USB modem functionality of the GP02 will actually work with the GP01 drivers just fine - though plugging the modem into the computer will result in the virtual CD-ROM drive with drivers and the manual popping up as with previous models.  Obviously the main WiFi functionality doesn't require any drivers to be installed at all.  Those who use the 3rd party Pocket WiFi Monitor software from Galapagos Software will be happy to know that it has been updated to cooperate with the GP02.  That said, a quick search showed that similar tools for Android OS have not yet been updated for compatibility.  

Previous models accepted a MicroSD Card, but only presented them as a USB flash drive when plugged into your PC with a cable.  This always seemed like a bit of an odd concept for a device marketed for its wireless capabilities.  It seems the people at eMobile (or, more likely, Huawei) finally got the hint, and added what they call "HTTP NAS" mode for the MicroSD card.  The old USB mode is the default, so you will have to log in to the admin screen and change the settings to try it out.  Unfortunately, while we thought that perhaps HTTP NAS might be a reference to WebDav (Which uses HTTP), it is nothing of the sort, so it can't be mounted as an actual drive in Windows or Mac OS.  How does it work then?  You can upload/download files from the web interface.  Note that you can upload, download, and delete files without even logging in, so anyone who runs an open access point might want to keep this feature off if they have secret files.  While we haven't tested this feature heavily, it seems to work as advertised.  That said, if you are constantly updating lots of small files, constantly uploading and downloading them from the device can be a pain.  Using it to store frequently used installers might be more practical.  As mentioned above, the card is no longer accessible without opening the device - which is probably a good thing, as it will prevent people from removing the card while the device is operating, and reduce the chances of data corruption.

The WiFi now supports the 802.11 N standard.  You might be thinking that even the theoretical maximum cellular speed of 42Mbit is still well under 54Mbit limit of 802.xx g/a, but there is another reason why offering N is important.  When you connect multiple computers to the network and want to transfer data between them, they are limited by the speed of the modem's WiFi.  By upgrading this, PC to PC transfers will speed up considerably.

With the exception of the aforementioned MicroSD related functionality, the web administration interface hasn't visibly changed much from the previous version.  (Though it seems that its inner workings have changed considerably since it broke all monitoring software).  One addition is the "Notifications" section, which will show incoming SMS messages from the carrier.  At present, eMobile doesn't send such notifications, and in our testing, we were not able to send SMS messages to it, even using an eMobile phone.

So what about the speed?  Speed is the major selling point of this unit, so if it's not actually any faster, there's no point, right?  Measuring the performance of mobile networks is fraught with many issues. Latency and bandwidth change from second to second, between locations, and across time.  The situation is much more dynamic than with wired networking, and the actual speeds achieved are usually only a fraction of the rated maximum speeds.  

That said, while you shouldn't expect to actually get 42Mbits at any average locations, the GP02 does seem to actually get around twice the bandwidth of the GP01 when tested in the same locations.  For example, one location where the GP01 typically gets 4-5 Mbps, the GP02 tested with 10-12 Mbps over several tests.  In almost all locations, we got at least 6mbps, reflecting the fact that the unit can pull down reasonable bandwidth even under poor conditions, due to its use of multiple cell towers instead of just one.  Even in particularly bad locations with a weak signal, we see nominally increased speeds with the GP02.  We selected a spot with poor reception inside a concrete office building, and we got 3.5Mbps on the GP01 and 4.85Mbps on the GP02.  Uploads seem to be around the same speed as the GP01.

In fact, a more interesting question than the "maximum" speed would be "What is the minimum speed you can typically expect to see?"  The minimum speed is, after all, what affects your ability to use services.  In order to use Skype, Facetime, youtube, internet radio, etc., you need a certain minimum speed and reliability.  The good news is that most of those things already worked fine on the GP01, so of course there are no problems on the GP02.  Large iTunes downloads and similar things do download considerably more quickly.

In the end, eMobile is constantly upgrading both their network, and their modems, so upgrading from the last generation to the current one isn't likely going to change your life drastically, but if you haven't upgraded for a while, or if you are looking to squeeze every last drop of speed from the network, then the GP02 may be for you.  In particular, if your previous modem is paid off, it makes a lot of sense to upgrade, because your monthly bill will be about the same, no matter which speed you are using - so you may as well get the faster modem unless you are planning to cancel your contract.  Since the GP01 is honestly good enough for most people, we expect that the GP02 will be mainly popular among new subscribers and power users - however, upon checking with a local eMobile shop, a large number of customers were there upgrading.