Hunted for hours on this one.
I wanted to be able to do some fine rotation of some text to align with some lines I have in a Visio 2007 drawing.
The standard rotation tool seemed to only allow me to rotate text thru 15 degree intevals and I needed more like 9. Turning off SNAP under Tools|Snap and Glue seems to only affect object movement and not rotation.
After a bit of searching I found this article
which offered the right advice.
If you select the text object you want to rotate and choose View|Size and Position Window from the menu bar it pops up a position dialog box for the selected object and you can enter an absolute angle value in this box to get the perfect alignment that you need.
Additionally the article above indicated something I definately did not know and that is that if you move the mouse/cursor further from the rotation point you can get finer rotation granualarity. In my case if I moved the mouse/cursor about 3 inches from the rotation point then I could rotate my text in 1 degree increments. Perfect.
Handy to know.