What is an unlocked cell phone?
and
As a T-mobile subscriber, do I have to buy only their phones or will my sim
card fit into other phones?

I was thinking of upgrading from my Moto phone to a new, PDA style
phone, possibly G1, and am wondering if I could use the same SIM card in
the new one without losing any of the functionality in the new phone
that would come with a new SIM card. I know I can store phone numbers ...

Marian Seltzer buried her late husband with his cellphone fully
charged. Now, three years later, she still pays his Verizon bill
monthly and leaves him frequent voicemails. He, uh, doesn't get them.
Marian even went so far as to etch his cell number onto his

Guy at T-Mobile booth in mall told me that there is new firmware
available (dated Sept. 18, IIRC) and that disconnecting and reconnecting
power should result in automatic upgrade.
I did, it didn't.