Update - I just installed beta 4, and the keyboard issue seems to fixed. I have to perform a restart to be 100% certain, but I think it is good now!

Yaaaaay! It is fixed in the beta 4 release!!! (That was driving me nuts!)

I commented in another post, but yeah, same thing here. The brightness does not go above 1. I can turn it down to off, but soon as I go the other direction, the first increment turns it on to low, and then ticking it up additional increments has no effect. It just stays dim. I had no idea how annoying this would be!

Yes, you are NOT alone! I tried everything, including resetting the SMC and no luck. Mine is a macbook 12", so the issue isn't confined to just one model.