Some good information here - thanks a lot.
You're right about calling other networks. If I call my friends on their mobiles (Orange), they either charge me 5p a minute, or take it out of my free minutes. If I call my brother, who's on Vodafone, it costs me 35p a minute. However, the Office of Fair Trading (don't know US equivalent, sorry!) are going to clamp down on this.
I don't think 3G can be compared to GPRS - here in the UK the providers are advertising GPRS as a kind of enhanced GSM (e-GSM) which is more like 2.5G rather than 3G. To me it looks expensive even though you can get 112kbps through it - Vodafone and BT Cellnet are offering it, but you pay by the amount of data you download.
Yes, 3G is also known as W-CDMA - but in Europe (and I think all the countries with GSM) it will be called UMTS (Universal Mobile Telephone System).
I think that FL is quite a bit larger than the UK actually! But what you're saying about market penetration is quite interesting.
One of the major reasons why mobiles have taken off in the UK is Pay as you Go. This is where you buy the phone for about 100 pounds and you then 'top-up' your call credit with vouchers. It's ideal for children and people who use it in an emergency as there is no contract required, and no credit check. Calls are slightly more expensive though. You can buy the phones everywhere - from supermarkets to airports.