I'm a little tore up about it. I think that many, if not most, issues are carrier specific. Take the JellyBomb theme as an example: you have different flashes for different carriers. Someone has a problem, and it's almost impossible to help them out, if your on a different carrier and have no knowledge of thier issue.
The reason I pointed out the theme, is that, traditionally, themes are not carrier specific, but they can be better tailored when they are. Just my2 cents.