Wit the help pf Xgraph, you should have for a normal machine load (i.e not encoding Divx !):

CPU-T diode Temp: 40-60 C° (above 75 C° =not normal)

Hard Drive Temp: 40-55 C° (hard drive temp above 65 C° can damaged the hard in a long term)

Fans speed: Defaults for Revision A-

1500 CPU
1800 HD
1240 SYS


If something like (A350 take off ;-) )
CPU - 3206 rpm
Hard Drive - 4406 rpm
System - 3325 rpm

not good...

The AppleDiscussion thread on it
here

Phil