I'm using both WiFi and Bluetooth with my 2210. As I use my PDA in a few different ways I find it nice to have both. I didn't go for the 55XX series as I prefer the samll size and lighter form of the 2210.
The bluetooth is OK for surfing but I don't find it as fast as the WiFi. Also, I can use the bluetooth with easySMS (
http://www.siedler-net.de/WinCE/easySMS/) and still surf via WiFi without impacting the perfomance or either.
Personally, I like the flexibility of having both.