I've been using SMC Fan control with my RMBP since I got it. For me at least, no interference with the mac taking over to raise fan speeds when it gets hot. I just have it because with or without it, lion takes a LONG time to do anything to raise it. I'll hit 200 degrees F before it even starts upping it usually. I ended up putting it back on since even if it can't monitor the heat (I have Temperature Monitor installed for that) at least I can proactively fire the fans up to max if I know I'm going to do something that's going to create a toaster on my lap. But if I don't change anything manually the laptop still speeds up the fans on its own. Just not as quick as I'd wish (again, same delay even without smc fan control installed).