I've given this a lot more thought than was probably necessary (or healthy), and there are only two things that are proper dealbreakers for me:
- Really thin necks, front to back. I used to own an old Rick 4001 and a Fender Geddy Lee, both had very thin necks which gave my hand cramp.
- Silverburst
There are a lot of other things I dislike but they're generally easy to change.