I think you would be an idiot to buy any i7 but the 920 at the current prices. Why would you want to spend $720 more for 600 mhz difference when you can easily get 3.2 ghz when you overclock the 920. I don't even think you would need an after market cooler to get 3.2..
Some people have the budget to spend up on the 975, and they don't want to spend time troubleshooting crashes and BSODs by overclocking. Not everybody is an overclocking gamer; some people have serious media applications that benefit from the 975 over the 920, and overclocking can be intimidating.
If I have the budget, then I'd be an idiot to buy the cheap processor just to tinker with BIOS settings to replicate the performance that I can get from the 975 out of the box. Having some money doesn't make somebody an "idiot".