I use the Space Navigator in Photoshop all the time, zoom, pan, and now with the Beta version I've managed to get rotate canvas to work.
I spend hours and hours editing photos (professionally), and use a combination of inputs as follows:
The Space Nav noted above,
Intuos 4 8x13 for drawing, and use the ring mostly for brush size
Use the spacebar, and alt,ctrl, shift keys for their modifier functions
Mouse for navigation
And for heavy sessions I use voice contro!l
- using the free software VoiceCommand from Killers Software see here http://www.killerssoftware.com/
Typically used by gamers, it is a great help in PS - I just ask for the tool I want, without moving my pen etc, plus other actions like save the file, selections, run actions and so on.