The Celeron is a cut down version of the Pentium with less cache memory and is subsequently quite a bit slower.
The actual CPU speed is not as important as the performance.
I'm an AMD fan, as an example I have a Athlon 64 3500+ and it only runs at 2.21 ghz but because of the design it runs at approximatly the same performance as a Intel Pentium 4 3.5 ghz even though the clock speed is only 2.21 ghz.
The new Intel Dual Cores will be a huge boost. My Athlon is probably about twice as fast as your Celeron.
Have a look here for the comparisons of the newer chips click here