Beaver is okay. It's nothing like the White or Norfork, though. It has been improving lately as far as fish size, but the main problem with fishing it is that it's BORING. There is very little flow most of the time, so it's kind of like fishing a lake. There are a few areas (Parker Bottoms) with shoals, but not many. I live about an hour away, and I rarely fish it (I probably haven't fished it in 3 years). I'd go to Roaring River before I went to Beaver, especially once the "off season" hits. The Catch and Release area is good quality, uncrowded fishing and offers the occasional hatch providing opportunities for dry fly action.
Here's a good board on the area if you start doing a lot of fishing in northern Arkansas:
http://flyfishingarkansasandmissouri.yuku.com
I should add that I rarely fish for trout any longer and do most of my fishing for warm water species, so my knowledge of the trout fisheries isn't as current as it once was.