I thought the cover was above average.. can it be improved? Yes.. Will it make a big difference? I don't think so.
The reason I say that is, word of mouth and book critics probably have more of an effect on selling books. If someone or some entity were to endorse Steve's book, then people won't really care what the cover looks like. i.e. New York Times or Oprah, etc...
It reminds me of Steve's most recent article, where he mentions that other bloggers may have a better looking blog, but he's capitalized on getting his blog functional first (with content and good article base). In the same way I think Steve's ideas will sell themselves, regardless of the cover. Most of you have already mentioned, that you'd buy the book anyway.
Also, another avenue is the internet marketplace. Most people who purchase off the internet will probably be either sold by the reviews of the book (5 stars, critic review..etc) as opposed to cover design. As someone indicated earlier, I also think that the title plays a big role as well.. in which the phrase "Smart People" in the title will definitely be catchy..
Nevertheless, Steve, I wouldn't worry too much about the cover, your content and word of mouth will help the book sell itself... and you can change the cover if you want on the 2nd edition..
