Is it worth it to upgrade my I7-970 to a new sandy bridge I7-3930K?
"Worth it" is a relative term. $570 + $200 on the mobo is hardly worth it for whatever performance gain in gaming. Whatever performance increase you can get from multi threaded application is probably something you can afford to miss. But if you are itching to see 12 threads in task manager & you got the budget, of course it is worth it.
To be honest, I dream about the 2011 platform just for that simple reason, nothing more...