Hmm, my personal opinion is no.
I did some research and found several different sets of Benchmarks that pit a Q9650 (3.0Ghz) against a i7 920 (2.6Ghz), at stock clocks.
And they trade blows. Upto 10% performance gap either way depending on the tests. More system memory intensive benchmarks favoured the i7, those relying on CPU grunt, the Q9650.
If you chuck overclocking into the mix (both chips are known to do upto around 4ghz on average), then the Q9650 advantage will dissapear in the non-memory tests, but still would be within a 10% margin I estimate.
So for me, my opinion stands as a firm No if your upgrading from a Core 2 Quad, but a Yes if your buying a new platform. Even then I would consider i5 first, unless your going multi-GPU in which case you want X58 and i7.