Hey fellow ZJunkies. I just found an undocumented ZB Navigation Feature (at least i think so, as i have never seen this feature mentioned anywhere).
Instead of rotating your model like you are used to, hold shift first, start rotating your model and then let go of shift. Your model will be rotating constrained to one axis. 
Really helpful sometimes.
Nice! I just tried it thinking “I could do that all along” then I realized it constrains the rotation to the axis of spin that you initiated. It’s actually pretty useful. Never knew that until now.
The other day (after almost 8 years of using this software) I just now found out you can zoom your model by holding alt while tumbling then letting go of alt while still holding the mouse down. This is another handy trick to add, thanks for sharing. Sigh all those wasted years not knowing these two little tricks.
… tell me about it
woooooow, there’s been so many times i’ve wanted to do this, thanks for the heads up.
Actually i found out the other day that it is documented in the shortcut list: http://www.pixologic.com/docs/index.php/ZBrush_3_Shortcuts#Mouse_Actions
But honestly … who reads this 