Ctrl (in Windows) while orbiting lets me turn my model every which way! Fairly useless as an architectural user but a boon for modellers who make widgets. Doh!

@rv1974 said:

The 'Lock\unlock aspect ratio' at material edit drove me crazy for years.
Clicking it wont change visually its state (stupid bug!). To see it changed one should move
the cursor off the button.

This one got me very frustrated, until I discovered it's just a slooow button!
In Windows 7 at least, click the Lock/Unlock button and WAIT for a couple of seconds. Lo and behold the button icon changes!

EDIT
Hmm. I'm wrong, you're right! The cursor does need to be moved off the button. As you say, stupid bug. Perhaps I'm a stupid bug..r