I would have to say an overall no. Performance-wise, you would have to be using specific applications to take advantage of them.
On the bright side, i7s OC much easier. They use DDR3, which is starting to drop in price, whereas S775 DDR2 is climbing in price. S775 will become obsolete much quicker, so if you need replacement parts they will be harder to find.
Don't think of it as having bought a 2011 Mustang vs. a 2004 V6. Both systems would have cost your roughly the same amount of money.
Now if you threw away the 9300 system to buy a i7 860, then yes, bad decision.