Can't comment specifically on that phone, but I recently bought a SPV C500 (orange pay as you go) which I unlocked immediately, flashed on the i-mate firmware and then used happily with my O2 SIM!

Apparently on the SPV you can use both bluetooth GPS and headsets at the same time, I know lots of other windows mobile devices don't support this.

You best bet would be to check the pocket gps forums as they'll be able to tell you what you need to know.

I have to say, I wasn't altogether convinced about a phone based on windows mobile, but I'm pretty impressed. The dialing is the best I've ever had on a phone, and I like the small form factor of the SPV - plus it's got real buttons! I know people experience lockups with it when using it a lot, I've yet to have a single one, but I only ever use it as a phone or as a sat nav device and don't tend to play with all the options.

Another place to check is the modaco forums, they have lots of information over there.