I went from an i7-920 @ 4.0GHz to an i7-3930 @ 4.8GHz. I am not a big gamer but a high-end imaging user (some gaming, some video editing too which makes choosing things complex). Yep, I had to upgrade from a 1366 MOB to 2011 (Asus Rampage Extreme IV - sweet board). I also upgraded to 64GB or RAM (from 24GB, and yes I use that much). and went from a pair of SATA II SSDs in RAID 0 to a pair of SATA III SSDs in RAID 0.
For my imaging work this build blows away my i920-based system. For gaming, no real difference unless I get one or two Titan's or 690's, but since I am imaging mostly I am going with Firepro V7900's for a full 30-bit imaging pipeline along with my new 30" Dell Ultrasharp U3014 - which is in itself mind blowing.
Full build and pics here:
http://pcpartpicker.com/b/BHn
Regards,
Mike