1) PSD files don’t have previews. I see some generic 2 columns of text. JPGs and TIFs show a file preview.
Where? In the Finder or in Bridge?
2) Even more annoying, my prefs don’t stick.
Is Photoshop crashing on you? Photoshop saves its preferences when you quit the application in an orderly fashion. If it’s crashing on you, or if you’re force-quitting it, prefs won’t be saved
What have you tried so far? Trashing the prefs files? Repairing permissions? Running Disk Warrior? Creating a fresh new account and logging in as a different user to see if the problem persists or goes away?
The finder for previews. Bridge is a charm but sometimes I just need to see one specific file.
I run DU as needed. Maybe the force quitting. I noticed at the end of the day when I’m leaving (I like to quit all apps) a lot of suite apps don’t quit or take forever and I have to go and force quit. Maybe I should just leave the apps active or let them take their time quitting.
Force quitting screws up a lot of stuff. It should only be used as an absolute result and with the understanding that you’d better do some serious maintenance after using that command.
All Adobe apps (and other ones too) write their preferences and changes on regular quit and not before that (including InDesign), which is why it sometimes can take some time to quit. Force-quitting unnecessarily is a bad habit which can not only screw up preferences but also the application itself in the long run. Should only be used if you are really stuck and application won’t quit after several minutes waiting or if it says "not responding" in the force quit dialog.