Its been interesting participating in what has essentially been a three year experiment by one vendor to improve their proprietary solution (I think there were two firmware downloads yesterday, to what ends I have no idea). Back in the beginning it really sucked, only 2mbit total channel bandwidth and zero-nines reliability. Downtime was frequently hours, and occasionally days. Things are much more reliable now thanks to weatherproof antennas up on the mountain (good thinking for a facility at 11,000 feet) and every server box has hardware watchdogs and remote resets. The employees at Niles Radio got tired of driving the snow cat up the back of the mountain at 4pm in a snow storm when a box got stuck (a regular occurrence).
Still, I'm glad 802.16 (and 802.16a) is finally coming out and I would switch to it if it weren't for the possibly that DSL is going to finally reach out here in the forest. 2.4GHz has gotten awfully crowded and I have more faith in an industry standard than the experiment in process from a vendor I've never heard of. I find it funny however, that people are worried about making it support roaming "like cell phones do".
The original 802.16 specification did not specifically support mobility of client devices. It does have an adaptive PHY layer that can shift modulation schemes on a client-by-client and frame-by-frame basis. Given low ground speeds, this adaptation alone might be sufficient to sustain some mobility. However, there is no provision at all for cell-like handoff in the 802.16/a specs; a single base station is assumed at all timesFirst of all, battery life for a portable transmitter/receiver that has to reach up to 40km away is going to be pitiful unless we're talking about plugging into your car, but the comparison with cell phone service is flawed on the other side: assuming that data services from cellular providers can roam.
I don't know about GPRS, but I have used Sprint's CDMA data service in a mobile application: I spent two and a half hours on Amtrak from Chicago to Champaign doing web and chat on my laptop with a friend's hotwired handset. About once every 20 minutes the signal would drop off to zero and I'd get disconnected. I then had to "redial" and connect to another tower which was at full strength.
If that's the competition, then I don't think 802.16 (or 16a) has anything to worry about it.