https://www.youtube.com/watch?v=g0DdGmmFaAs
This is an almost 40 minute video but it's actually a good watch. He does a good job covering some pretty common engines and their common problems that HE sees (he clarifies this several times). Make sure to watch all the way to the end...
I had to get pretty far in but eventually I got my Briggs opposed twin fix and the verdict is that they are good. Yay.
Actually, in summary, what I really got out of it was that both Briggs (Intek and related) and Kohler's (Courage) cheap engine lines have a lot of common issues, and the more expensive lines do not. This isn't really shocking, is it?