Yea... upgrade! WM will be a bit of a shock to you, it's quite different than what you're used to in terms of mobile telephony. The Kaiser would be a great piece of technology for anyone to own, however the price tag may not be everyone's cup of tea. Personally I plan to get an unlocked one for some 800 dollars. ATT may offer it for 500 with 2 year plan. As for unlocking, if you have international travel ahead of you in a near future then I believe there is a SIM unlock solution already. If not, I wouldn't worry about it until you need it unlocked.
I see dead phones, calling around just like regular phones.
My cell phone history: Ericsson GH788, Mitsubishi T200, Sanyo BAM 201, LG V111, Ericsson T28, T39, T68, T68i, Panasonic GD87, GD55, Nokia 3660, 6600, Motorola V525, A360, Panasonic X701, Palm Treo 600, HTC Blue Angel, Wizard, Herald, Kaiser, Touch Pro 2, Doubleshot MT4GS