I guess I've been lucky. I've certainly flown with a few less than pleasant FOs over the years, but the vast majority have been great to awesome.

Off the top of my head, I can think of maybe 3 or 4 in my base that I try to avoid and only 1 that I absolutely will not fly with. All of them are known problem children. There are a few "premium only" folks that I will tolerate for 1.5 pay, but not many.

Of my top 3 "avoidance" FOs, one moved, another upgraded (and will be in another base for the foreseeable future, unless he comes back as an FO, which happens pretty often in my domicile) and the one mentioned in an earlier post is still around.