Also I've heard the previews in Magic Bullet Looks are now inverted.
It seems Apple was tweaking some plugin related things in 10.0.4 so those seem to be where one might find issues.
I have both Looks and Sapphire Edge but I've been too busy to beat on them.
I have FXFactory as well and didn't get any crashes relating to that though.
I'm hearing that Broadcast Monitoring is working well (although still not perfect) as Blackmagic and I believe Matrox and AJA have updated their drivers with 10.0.4.
I was working on a job which used the RC of NeatVideo which they allowed me to purchase even though not official release and again while I didn't test anything, that project behaved when I opened it.
As others are reporting it is behaving a bit snappier and seems to have solved the beach balls. People are noting some changes with preferences and apparently sliders on some things. Basically it seems this was a major, not minor, stability release.