1) The camera often spins away from what I'm trying to zoom in on. This is an old and *very* frustrating bug.
2) When rotating or moving prims, sometimes they disappear until you stop moving them. So, how do you know when to stop moving them? You don't.
3) The numeric entry fields for X/Y/Z size and position and path cut refuse to allow some values. You also can't drag prims to some locations. They snap back. Same with using the up/down arrows on the fields. They snap back. It is currently impossible to precisely position things without a script. Unless you can avoid (if I recall) an even number in the second decimal place.
4) Sometimes when you select a prim in edit mode, it rotates a bit.
5) Sometimes you can't de-select prims in a multi-selected or dragged set by control-clicking them. So, sometimes you can't de-select and re-select a prim to make it the root prim for linking.
6) Sometimes when you go into edit mode on a worn object it disappears. To make it re-appear, take it off and wear it again.
7) Sometimes when I click the blue arrow attempting to move something along the Z-axis the camera goes into a slow spin as long as I have the mouse clicked.

9) Sometimes when you un-do a rotation your root prim separates from your object and is rotated at a randome angle. See #8. Combine these three rotation bugs and rotations are very dicey. Definitely take copies often. That can't be good for the asset servers.