When in the debugger, open Robot->Debugger Windows->System Parameters.
Look at the aveBackgroundTime. I don't know exactly what it means, but I think it correlates to the CPU usage of the NXT.
FTC #248: Fatal Error, programmer, Drive team
FRC #3142: Aperture, Lead Designer, Lead Programmer, and Lead Builder.ZR
#89: TBD, programmer.
And I help three FLL teams.