I'm looking to go from an iphone to a Driod. At&t has an app that is very mobile friendly and signs in automatically... I really like it to see what my usage is and pay my bill by, pointing and a click.
Verizon has a "My Account" app in the android market. I haven't used it, but I assume you can use it to log into your account and pay bills, look at plan, features, etc.