I'm not troubled by the lack of global roaming, but I often use my iPhone with a headset, while checking e-mail, web, apps, etc. I'm assuming this is a nonissue with a wifi connection - data over wifi; voice over CDMA.
GSM has several advantages over CDMA– namely the ability to provide simultaneous data and voice connections plus international availability. For many users the lack of international support for CDMA won’t be a big issue but the lack of simultaneous data and cellular connections could be a big problem.
Verizon iPhone users will now have to make a choice – voice or data. Using your voice connection means no Internet connection and no app usage for anything that requires a data connection, ouch! Want to look up the address of the restaurant you and your friend are talking about?