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You're likely to benefit more from 8GB RAM and a good solid SSD than the CPU. I recommend upgrading those two and then wait for next major update.

That's exactly what I'm doing. The two aforementioned upgrades go a long way towards speeding an MBP up.
 
I'm doing a lot of layers and using filters such as Nik's Viveza, OnOne Filters, and Topaz Filters. Once I started using filters the system really slowed down... Too slow now! I've got a buyer for my 2007 MBP 2.4 for so just debating whether to get a MPB 2.66GHz or splurge on a Mac Pro 6 Core 3.3. If the MPB 2.66 is significantly faster that should suffice for now until the Sandy Bridge chip comes out next year, and I'll do the Mac Pro then.

A mac pro will be faster than any laptop in the next 3-4 years.

Even an imac i7 will.
 
The i7 is faster at any usage at any point in time in the history of computing. If you still don't believe all of us this article can explain how and WHY the core i series blows the C2D's away.

And just for some reference, the 2.4ghz core i5 is faster than a C2D 2.8 Ghz. They are just far superior.

Actually that article is a POS and not even relevant because it discusses the desktop Core i7, not the mobile architecture, which is significantly different.

To the OP, I would expect to see around a 40-50% improvement in certain CPU bound tasks. I went from a 1.66 C2D to a 2.4 i5, I notice a big speed increase, but Lightroom is still slow at creating previews (with an X-25 SSD).

WRT RAM upgrade - use activity monitor to see how much RAM the app in question uses when it's processing its stuff - if this is large (say >1GB, then 8GB of RAM might be wise, else, for <1GB processes I doubt you're memory limited).

Perhaps you could drop by an Apple store, see if they can install some SW on a demo machine and run a little test? That would get you a definitive answer...

Is your time == money? If so it might be worth to upgrade.
 
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