If you don't plan to use BB Messenger, you are clear to delete it and the Tasks app, also. Those two are standalones, and a number of people delete them.
Posted from my CrackBerry at wapforums.crackberry.com
Yes its ok to remove those two apps without messing up your phone. Plus you can alway reinstall them in app loader just by selecting them on the list. Even though you remove them, they are still listed in app loader.
Posted from my CrackBerry at wapforums.crackberry.com