I have rooted all 3 of my past android devices (HTC Inspire, HTC Thunderbolt, and LG Thrill) I ran CM7 on my Inspire for a while and it was very fast and greatly improved my battery life. I currently still own only the Thunderbolt and it is rooted and running BAMF Sense 3.0. I am a heavy phone user. It rarely goes 10 minutes at a time without me doing something with it. After having used the SGS2 for the past 4 days I can say that the battery life on it is quite awesome, and you can remove alot of the ATT bloatware yourself. That being said I think CM7 is way too "vanilla" for me. I like tons of wiidgets and flashy animations. I like to switch things up often and running different launchers without rooting seems like a great option with this phone considering how fast it is. I get people are always looking to squeeze the last bit of juice out of their devices but if you are unsure or afraid of rooting I think this is a device that you really don't need to.