It seems, that I have a little bit of a longer render times with SR3 as well. The last scene, an enclosed room setup, I did with SR2.1, took about 1h 52 min to finish. The same scene with SR3 needed 2h 14min.

But, the IDL "splotches" were less noticable in the SR3 render, with the same render settings, so it's all good on my side =)