It seems that many of the issues that people have had with AP in MSFS is caused by not understanding how it works. I went through some tutorials and worked on it quite a bit and now it works for me very well.
The only bug I've run into is where, very occasionally, the thing will hold onto Alt even when I disengage the AP. It seems to want to control the elevator and ignore my inputs. It's happened a couple of times in several dozen flights, so it's not been a show stopper for me.