My 2500+ is running @ 2.17GHz (180MHz FSB) @ default voltage. With the case temp. averaging 31C, the idle temp. is 38 to 40C and 49C under 100% load (Prime95). I use an Alpha PAL 8045 with a Vantec Stealth 80mm fan to cool the chip.
I have had the chip up to 2.25GHz @ default voltage with a FSB of 180MHz. It was Prime95 stable for 14 hours and then I had to get my gaming fix. I may up the speed to that again when HL2 comes out, but right now I'm fine at 2.17GHz.
This chip is a good overclocker.