Will Unlocked GSM Phone operate Internationally?

[rrvo]

Will an unlocked, quadband, GSM Pocket PC work for international phone and data use when supplied with the proper SIM card for the country I'm visiting?

I travel internationally, but don't like to travel with a laptop, preferring to use my phone (Samsung i500, then HTC 6700, now HTC Mogul) for personal computing as well as web access (via wifi), e-mail, voip, etc., where and when available; relying on a separate, unlocked quadband GSM phone for standard phone communications when wifi is not available to my PPC.

I've been with Sprint (CDMA) for years, but would certainly consider a switch to a GSM carrier here in the States IF that means the possibility of converging my two overseas devices into one.

If some of you have some solid knowledge on the subject, I'd sure appreciate it if you'd share. (PPCG is really great at that--your kitchens have made both of my PPCs infinitely more usable, and I really appreciate the expertize I've found here.)

Thanks!