I've pre-ordered the BB Storm and this is how I assume it'll go with a new Android phone
1) Pre-order on their website
2) Phone arrives are your house on the release date (usually)
3) Dial #228 and activate your phone
4) Log-in to your GMail account
5) Surprise, everything is on your GMail account. Your paid apps, contacts, calendar, and any other goodies you have. I'm not sure if free apps are saved on there. I ROM'd my OG Droid over to GPA 19 again yesterday and surprisingly I had the same wallpaper before the reset and the same free apps AND it had remembered my wi-fi password. Different people say different things. I deleted all content off of my phone so that must mean GMail backed everything up. Of course that means contents on the SD Card will probably not be able to get transferred via GMail. sad face.
TL;DR GMail saves everything and transfers your contacts, calendar, paid applications, and in some cases you get extras like your wi-fi password and old wallpaper. It's as simple as that!