indeed. there's significant performance increased using c2d compared to p4. i'm using e6300 overclocked to 2.1ghz without significant heat increased! i even can make render farm using 3 virtual pc without performance penalty, render time speeded up almost 3 times without sign of cpu being overloaded.
there's also significant speed improvement in photoshop too, especially when using 3rd party filter like alienskin. time to apply filter decreased drasticly. last time i applied waterdrop on 1600x1600 texture, it took about 2 minutes in my old p4 3ghz. now it only took about 10 seconds!
and don't ask about game performance. in my old p4 3ghz, i got only 25fps fastest framerate in flight simulator 9. this one, using the same graphic card (ge6600) framerate boosted to 3 digits (100fps above) and the variation ranged from 50fps to above 100fps. i have to limit it to 30fps so tha game could playable smoothly because that far fps variation range can produce stutter.
i'm really pleased with this cpu, especially to its low power consumption & radiates less heat (40 degree centigrate on average load, 36 on idle, 45 max load on 30 degree room temperature). if you have more budget, get the e6600, you won't regret it