It's funny, I have a T68M and have been lusting after the P800 (if it was available in the US I would have bought one already), but just noticed today that iSync supports the T68M. This will make my life a lot easier (as soon as I shell out the bluetooth $$$)
However, I'd still rather have a P800. I've got T-Mobile and GPRS service right now. Did you have any problems getting your phone working with your T-Mobile account? Did you just have to plug in your GSM card and go? Does T-Mobile support the P800, or in any way mind that you're using it?