Not worth the upgrade then if you are already running SB or IB
I really wanted to upgrade but it's not worth the money or hassle to go from my 2500K to Haswell.
My last upgrade was from a Q6600 to my 2500K, and that was a huge! I'm not expecting my next upgrade to be as big as that was, but there is not enough real world difference to go from my 2500K to Haswell.
Haswell would be a good upgrade from an old AMD setup or an Intel 775 or 1366 setup though.