This is what I think:
Temps
With the top of the range air coolers/H100 or custom water IB will be fine running overclocked. I wouldn't be surprised if anything less than custom water cooling had trouble with the IB 3770k under stress conditions but very few people will be in that situation for everyday use so ultimately I can't see temps being an issue for most overclockers.
Performance
You will probably run IB at a lower clock than you would SB, but IB will perform better clock for clock so IB will probably win by about 5%. If you are running on custom watercooling then you will probably be unhindered and can take IB to its limits giving maybe upto 15% extra performance over SB.
Chipset Features
PCI-e 3.0. Meh, makes no difference for single gpus. If you sli/xf the latest gen then you will need PCIe3 support to avoid bottlenecking the cards. If you run more than 2 latest gen cards then x79 is the only way to go.
USB 3.0. If you use USB 3.0 then obviously this is better, if you don't then this makes no difference.
Lucid MVP. Can see some performance gain in games dependant on which ones you play and at what resolutions. Can make a big improvement in fps, none or make it worse. Can also reduce power consumption which certain uses might eventually notice on their electricity bill. Again, not a deal breaker for me.
Price Vs Performance
IB and the z77 are *slightly* better than SB z68.
It's all down to price for me, I'll willingly pay up to 15% more for a IB/z77 setup than an SB/z68. If it costs more than that then I will be snapping up SB. SB is still so very good that I have no issues with that at all.
You can of course mix the technologies, the most sensible way I think would be SB on a z77 if you wanted the z77 features but prefered the SB cpus for heat/money.
If you need more performance than an SB cpu and/or will be running more than 2 gpus then 2011 is still the only way to go.