I agree. Rather than rainbow the brackets I think a better solution is to highlight the matching brackets with a temporarily different color as user moves the cursor.

Or at least make it easy to turn the rainbows on and off.

which forces you to read everything individually and not miss something. I prefer less highlighting for this reason. I highlight a few keywords but other than that I don't highlight. I find it helps me _read_ the code rather than skim the code. (and for skimming, I'd grep through it most likely looking for something specific rather than trying to understand it.)