Is the i7 2.2GHz MacBook Pro worth the price difference with respect to the 2.0GHz model?
I bought a new 15'' MBP just one week ago and I considered the same choices. Finally I took the 2.0 GHz for the following reasons:


from the pure CPU point of view this would be an endless pursuit: there will always be a CPU with a frequency a bit higher than what you have; for example you would be tempted to go from the 2.2 to the 2.3 GHz


the 2.2 (and 2.3) have 8 MB (instead of 6 MB) of L3 cache, that's my only regret
I think it is more useful to upgrade from the 5400 RPM drive to the 7200 RPM, I think there's a noticeable difference
if you're a software developer then you should really consider to upgrade to the HD screen



In my opinion, unless your budget is unlimited these two upgrades are much worth their price than the CPU upgrade to 2.2 GHz (even considering the GPU and the cache).