The new 2.2GHz CPU will almost always be faster than the old 2.33GHz. The 20% faster FSB is a much bigger deal than the loss of 6% clock speed. The new chips also have some other enhancements, including being able to clock the cores separately, and sort of overclock one while reducing the other if you're running a single thread that's hitting just one core hard.
And of course the new ones can use at least 4GB of RAM (quite possibly more once larger DIMMs are available). And they have a massively better GPU, which may or may not matter much to you, but it's certainly a nice thing to have something that could conceivably last a few years longer.
Oh, and of course the new backlighting that most people seem to prefer (and should theoretically last longer, not that CCFL doesn't last a long time.)
There's no way I'd get the older 2.33GHz system unless it was discounted several hundred (at least) below the current 2.2GHz system.