As someone who spends their time equally between the US and Europe I had no choice but to choose a GSM carrier (Cingular) for my BB.
I didn't consider Verizon or Sprint due to their inabilty to allow International roaming with a BB. However if they introduced a BB locked to CDMA in the US that allows International Roaming with GSM I would consider them.
In Europe a phone's SIM will be locked exclusively to a carriers Network when in the "Home Country". Even when there is no network availabilty it won't allow you to roam onto an alternative network in your home country. If the phone isn't locked to a network you can change the SIM for one from another Network and use it.
In a similar manner if you get one of the Verizon dual CDMA/GSM phones (Which has a SIM) it doesn't allow you to Roam onto Cingular or TMO. Therefore I wouldn't expect a dual CDMA/GSM BB to either.
Verizon & Sprint are missing a great big chunk of income from not offering International roaming.
I belive it will come - Nextel took the step to introduce iden/GSM phones to tap into the international market. Then we had three different GSM standards with the US going for 1900 and the rest of the world on 900 or 1800.
A few years back the GSM operators outside the US sold handsets that just worked on their own frequency 900 or 1800. However so as to maximise their opportunity to earn revenues from roaming they worked with manufacturers to develop and sell dual band phones.
Once this became the standard the next market for income through roaming was the US. GSM was in its infancyin the US but Tri-band phones became the norm. These have now been suplemented by Quad band.
All 3G (WCDMA) phones are a minimum of Triband. I have just got a Nokia N80 which is in theory six-band GSM -EDGE-EGPRS 850/900/1800/1900 and WCDMA 1900/2100.
The first BB device to work on both GSM and WCDMA has already arrived - The Nokia E61 and is being sold by the WCDMA network "3" in the UK as well as on Vodafones WCDMA network.
The Japanese and Koreans have different standards again. Eventually we will see handsets including BB's being able to work with all given technologies.
First step must surely be dual GSM/CDMA devices.
Bit of a rant for a Newbie I know but as a gadget freak I have developed some strong opinions on technology. However these are only opinions and I'm sure there are many who believe I'm talking *%^!.