Review: Samsung Vibrant
The Vibrant supports most forms of messaging you expect to find on a device such as this. There is the native Android Gmail app, of course, and thankfully Samsung hasn't done anything to try to alter it.
There is also a separate email app for POP3/IMAP4. I couldn't get it to work at all. I tried a handful of POP3 accounts, and none of them were ever able to authenticate. I have followed up with Samsung about this issue and am still awaiting a response. This separate email program would also be used for an Exchange account.
SMS/MMS is supported in the "Messaging" application. This app works well. It offers threaded conversations, and if your SMS conversations are with a Facebook friend, you automatically see their profile picture next to each message. (Also true if you've set up a picture ID.)
The Vibrant also has limited instant messaging on board. Google Talk is a separate application and is the native Android app. Samsung hasn't changed it. If you want to use AIM, Windows Live, or Yahoo IM, you are going to have to take a stroll through the Android Market for third-party solutions.