The $5 GPRS plan from T-Mobile can, and sometimes is, quite restrictive. Typically, not all the ports needed for internet access are open, though at various times in the past couple of years they have been. For truly flawless access, the easy thing would be to use the TMobile WIFI/GPRS plan, which, while expensive at $39/month, would actually be cool with the N800, since you could surf at any TMobile hotspot, and use the GPRS connection through your phone the rest of the time. TMobile has no limits on how connections are used or what devices you need. In fact, any unlocked gsm cell phone that supports Edge and the 1900mhz gsm band will work on TMobile in the US.

I was just in Europe, and I took the N800 and my TMobile SDA, which is setup for bluetooth DUN. I was able to surf at Edge speeds in a number of places using the SDA has the modem. Of course data roaming is pretty expensive, and I ran up a $199 bill in a week! But, it did work.

I also use my Treo 680 as a wireless modem. I have to say that once you figure out the nuances of the N800 and its connectivity settings, it works very well. What I don't know if if you can surf using a bluetooth modem and also have a bluetooth keyboard connected.