[Pandaman]

Yes the TP2 is compatible with older SERO plans. I've had a SERO 1250 plan for $49.95/mo with unlimited data for over two years on a Palm Centro, and I recently upgraded online to the TP2. There was no change in my plan at all and in fact I got the phone for $199 plus tax and I didn't have to sign up for another two years.

Regarding the unlimited data, this doesn't include what Sprint calls "premium" services. As far as I can tell, these would be Sprint Navigation (only works free for 7 days, after that $9.95/mo) and Sprint TV (almost everything has a monthly charge). The Nascar and NFL applications both seem to work fine without restrictions.

So when Sprint says that the phone uses a "different type of data", what they mean is the "unlimited" data is different now because it includes these premium services.