Hello!
I also use a mac. Tooltips are extremely annoying if not implemented properly. The delay in sketchup is extremely annoying. If you take the mouse focus to another palette and back you have to wait another 10 seconds. There is no way to list materials(in the mat palette) in a text format(only icon)so you have to wait every time you go to the model window and back.
Please give us the ability to turn them on or off in a prefences button. Even GIMP does this. The ideal situation for SU would be pressing a key while hovering, only if I need the tooltip.
I also use Painter and they are on all the time, popping up with useless info 90% of the time, covering up what I actually need to see or click on.

Maybe the people at Sketchucation can get thru to Trimble! I have posted the Mac issues at least 20 times and I don't even get a response.

A note to developers:

Please don't turn them on all the time to compensate, unless you give us a way to turn them off. I will have to pay for another shrink visit! A 2-3 second delay is OK if this is the only option. The hotkey on mouse hover is the best solution. If you use 4-5 programs as a designer, Arch, etc. Icons become worthless. Who can remember which icon is what in which program. The only option for a professional is text lists or icon and text. I need speed not pretty icons.

In closing, having been 3D modeling for 20 years now, Sketchup is still my fav 3d surface modeler. The Mac version needs a little work, Though.