Spyder3Pro from Datacolor is actually 2 applications; Spyder3Pro itself, which is the monitor calibration program for Datacolor's Spyder colorimeter, and Spyder3Utility which co-installs and should run constantly in the background keeping tabs on the room's ambient light levels and alerting you to when the monitor should be recalibrated.
On a clean install of Lion on a late 2009 iMac, Spyder3Pro runs okay, except when doing a full calibration which includes setting the monitor brightness. The program should set the brightness automatically as part of the calibration, but under Lion it cannot do this, so you have to go into System Preferences and do it manually part-way through the calibration. Having completed this, the calibration then appears to proceed correctly.
The monitor application Spyder3Utility does not function properly at all on Lion - it terminates 10-15 seconds after launch without explanation or bug report screen.

Datacolor provides an updated version of the spyder3utility here:

http://support.datacolor.com/index.php?_m=downloads&_a=viewdownload&downloaditemid=183&nav=0

Copy the unzipped file into the folder (overwrite the old one).

Have a look at http://www.datacolor.eu/en/support/osx-lion-support/index.html

It works fine on Lion.