200MB is plenty enough, if you have Wi-Fi at home and don't stream music/videos all the time on the go, you'll never fill it up. In the first month I tracked my Data usage and barely filled up 300 MB with streaming music for hours on the go. If you download over Wi-Fi and keep in mind to download huge file packages over Wi-Fi (by that I mean start your games once while you are still on Wi-Fi, a lot of games need to download additional data on the first startup) you should have no problem. Just download something to keep track of your data usage for the first few months, as far as I know Gingerbread has data traffic limits inside the firmware, so you wnon't need an app for that, when it comes out for your phone.