Even though many many people here CAN do that, many would prefer not to. I have had the SGS2 for a whole 3 weeks and haven't rooted - I rooted my Captivate within a week.
Root and rom and you will have no problem.
Not sure why the device is so much thicker given the lower battery capacity. For anyone interested in this, I'd worry that it would have a very low battery life due to the use of LCD versus AMOLED.
I am pretty disappointed by the thickness of the Rezound. It's a beast specs wise, but it doesn't look like I'll be getting a slimmer device if I dump my Thunderbolt for it. Plus it has a lower battery rating than the Nexus and Razr so I imagine I will be compelled to buy another Seidio extended battery for it.