2007 GMC brake problem
 

I got my pickup the first part of June and the brakes were great. It had a nice firm and consistent pedal. About a month later you could barely touch the brake pedal and it would slow down/stop the truck. I took it to the dealer, they drove it and said it was ok. A couple weeks later the passenger rear tire stared locking up when you put descent pressure to the pedal and the brake pedal was higher and made the truck uncomfortable to drive. I took it to another shop he noticed the problem right away, the rear brake were out of adjustment. (has drums on rear) This cured the problem for a couple of days, now the pedal seems to be raising up again. Could a bad master cylinder cause an inconsistent pedal and cause the drums to adjust out?

Are the brakes getting weak? When you adjust the brakes, they have to reset, and the pedal can rise some before they stop moving. If it was me, I would put all new brakes in the truck.

I don't quite understand what your NOT happy about.
As time passes, brake pedals since and you need to press harder to stop. Your ride seems to be doing the opposite. :)
An accumulation of brake dust will also cause your rear brakes to become very sensitive and lock up on light braking.

It has new brakes all the way around, the brake have all been cleaned and the front caliper pins greased. The reason I'm unhappy with it is because it has pretty much zero pedal travel before the brakes engage.

there is a adjuster on the back of the pedal to adjust the pedal travel.

That's an really good solution been find out.