T Mobile WiFi phone access.

I just bought a Blackberry 8900 from T mobile. I was pleasantly surprised how easily I was able to receive and make phone calls through my wi fi (UMA).

1) I assume these Wi-Fi minutes count toward my monthly cell minutes?

2) I assume that if I sign up for T-mobile@home for $10/month these will not count toward my cell minutes?

3) I assume I could be anywhere in the world as I use this T Mobile wifi phone access?

4) I assume if I buy a T-mobile@home router it is an equivalent of a Vonage router (i.e. internet Ethernet one one side and RJ 11 phone on the other side). I could connect this to multiple wired telephones in my house.

5) I assume I can somehow port my home number (currently with Vonage equivalent VoicePulse to T-mobile@home).

Any ideas, obvervations, suggestions on T-Mobile @ home would be appreciated.