I don't know, 2.4 or 2.2 maybe. It depends on what you're doing, software that relies on clock speed or cache memory more. Office applications and such are Celeron's high point, but it's not that good in games.
Well I certainly didn't think it was that bad, wow.
If you're searching for a budget processor go with the Duron. I built a machine with a Duron 1.8 Applebred, and it was pretty damn fast for a <$400 machine.
I suppose the Celeron is what AMD fanboys stereotype Intel processors to be - lots of MHz and zero power. It's like biking/driving in 1st gear - lots of RPMs but you're not going anywhere.
When playing games a Celeron chokes up due to not enough Cache Memory. Soon there will be some Celerons with a 533Mhz Bus and 256k cache on a 90 nm die process.