[outerpip]

I have used both Handcent and Chomp, and I have to say they are both much better than the stock app. The main reason I use something other than the stock app is because Samsung was smart enough to not put a notification LED on the phone, therefore, unless I hear or feel the phone, I can't tell I received a message just by looking at it. Handcent and Chomp both provide a popup that will turn the screen on. Plus, you get options to personalize your phone a bit more. As for downsides I've noticed, they are a bit slower than the stock app, and you have to look at adds hidden around the screen sometimes, but it's not enough to keep me sticking to the stock app. And as Spik3 said, go into message settings, and turn off the Auto-retrieve and the Notifications checkmarks. No need to worry about uninstalling anything, especially if you don't like it and decide to go stock again.