I'm fine with anything as long as:
1) It has the right geometry to work properly. You'd be surprised how often this gets messed up, even by "The Greats". If it's a thumb stud and not designed to flip open via the thumb stud, then the whole throw of the blade should be cleared so that your thumb can control the thumb stud without readjusting in the middle. CRK is one of the few I've found that gets this right. I've had a few Spydieholes with similar problems. Flippers shouldn't require a physics degree to use properly.
2) It doesn't ravage my finger or thumb. Also extremely common (Spydieholes with sharp edges, thumb studs that slice up your thumb, strong detent and sharp edges on a flipper, etc.).
3) Needs to fit the overall design of the knife. Spydieholes get something of a pass here, because with proper blade shaping, they look great. Sometimes they look tacked on. All depends on the designer. With flippers there's a trend lately to go with these huge, pretentious, ugly flippers that just don't go with the flow of the knife. I know you guys have seen what I'm talking about. And there's lots of poorly designed thumb studs out there.
Yes, you can say I'm picky, and yes there is no such thing as a "Perfect Knife". But I think saying "all flippers are duuummmbbb" or "all spydieholes suuuucccckkkk" or "all thumb disks and/or thumb studs are stuuuupppiiiddd" is just ignorant.