Picked up an Android G1 last week. Spent more time than I should have angsting about Google Contacts, ended up cleaning up the SIM in the 6630 and pushing some of the more recent contacts back into it, then pulling that over.
I used to carry a Palm TX (last interesting PDA in a line that goes back to picking up a Palm 5000 at Fry's) and I think the G1 is a big improvement over that:
The TX wins on a few things:
update http://www.expansys-usa.com shows a G1 cradle available for order but not directly in stock...
The phone I used to carry is the Nokia 6630. The critical problem that led to the upgrade is that it's old enough to not have an 850mhz band radio so I have a lot less coverage than I really need, especially on New England road trips. Otherwise, the 6630 actually has some advantages over the G1:
The G1 has some specific advantages over the 6630 as a phone:
Note that I didn't mention 3G - first, the 6630 was one of the earliest "3g" (euro band only) phones anyway - second, I leave the G1 in 2g-only mode, because I live right where 3G service runs out - a block west of here, coverage (on t-mobile's own maps) vanishes completely, so actually doing 3G isn't really a benefit...
All told I'm happy with the G1 as both a new phone and a new PDA. Conveniently they fit in the same pocket :-) My only complaint in that regard is battery life (and it still lasts the day - but if the phone is to be believed, it does so only barely.)
(Next up: advantages of the combined device, google-syncing, and development...)