Have been running mine for a month now. Am generally very pleased with it. It means I can access high-speed mobile broadband almost anywhere.
Things I like:
1) HSDPA was a bonus. I had no idea this existed in the UK. Using it via 3's network (which I think has by far the best 3G coverage) I can get speeds better than my home's ADSL connection.
2) I bought it mainly for using with my iPad (wifi-only model), but of course the good thing is that all my wifi-enabled devices can use it (so it is more flexible solution than, say, an iPad Wifi+3G model, which does not yet have access-point functionality that other devices can connect to).
3) Spare batteries can be bought and swapped in on occasions when running out of juice in the field,
4) Small and compact.
5) Fairly straightforward browser-based UI.
6) I can send text messages from it, via the UI. Nice.
Things that should be improved:
1) I think they should have made it slightly bigger, so that they could fit a larger battery that lasts longer. The battery life is ok, but not quite as good as I had hoped.
2) Occasionally its connection to the 3G/HSDPA network hangs up, which can be corrected by a re-start. I am not sure why this happens, but what seems to be happening is that it tries too hard to maintain/regain connection when in a signal blackspot, and overheats; this causes the hangup. Unsurprisingly this happens most often when carried in my jacket pocket. By switching it off and on (which means it cools down somewhat) it resolves the problem.
In summary, a very useful gadget for the mobile worker.