For most bikes it's not a big deal to just spread the rear triangle when you install the wheel, but as Bob said, you should try it and see for yourself. I'll just contribute that my primary rider is spaced at 126, has a 130mm hub and I don't think twice about installing it. I do have an old mountain bike spaced at 126 that I squeeze a 135 into, and that is a chore.

As far as the brakes go, if you are close to having enough reach, but not quite there, it's not the end of the world if you file out the bottom of the slot just a little bit.