Worldwide there were 500 million more mobile users of all technologies at end-September 2006 compared with a year earlier. The GSM family dominated the marketplace, growing its customer base by 497 million new customers and increasing its global market share to 83%.

Over the same 12 months, CDMA technology also added nearly 50 million customers while other technologies registered a decline.

T-Mobile and Sprint are GSM
Sprint and Verizon CDMA
The most visible feature of GSM are SIM cards. SIM cards are removable, thumbnail-sized smart cards which identify the user on the network, and can also store information such as phone book entries. SIM cards allows users to switch phones by simply moving their SIM card from one phone to the other.
I am using both and the Sprint internet speed is about 5 times faster than Cingular but I don't think the call quality is as good.

Just wanted to throw this out.

Does Sprint use SIMS on some of their phones?
I do use a Sprint Broadband card, and I've been taken back at how well the network operates. I mean I do get some dial up speeds sometimes, but I can get online on my laptop at my house in OKC and drive to tulsa, without ever loosing a connection.

But I'm amazed at the overall growth. Craziness. :)
Good article upisgr8.

Chase Tower has a Sprint Broadband mast on the roof that gives wireless notebooks a network connection within a 35 miles radius.