The main negative impact that I have noticed is that when I overclock my N900, my video recording drop frames. With the stock kernel, the recording is smoother. I recorded test videos on a fresh flash of PR1.3 and then a fresh OC flash and the difference is noticeable. I notice the same with PR1.2.

I just can't let go of my need for speed in Mario 64 so I will have to deal with stuttery video recording....