Except there's a great caveat with this approach. People that are highly productive and self-motivated often don't give a pleasant impression because they are fascinated with the idea and don't care for the looks. And vice versa, those who will look like a great friendly team, will be passionate about, well, looking great and friendly. They will spend time getting together, having endless pleasant talks about the latest news and their favorite TV show and couldn't be bothered to get out of the comfort zone and actually deliver something measurable.
I think this is fine for excusing the social quirks of individual contributors. If you're talking co-founders, though, I'd consider this "caveat" a red flag. If a person can't bring himself to make a positive impression to other human beings because he's too enamored of the "idea and doesn't care for the looks," he probably doesn't have the requisite maturity to co-found a business that will employ people.
Of course, some people really are all talk and no action. But I suspect you're assuming too strong a correlation with social skills. The fact is that there are plenty of brilliantly social people who can and do execute, and plenty of smart introverts who can't. I'm not saying, "go into business with your friends!" I'm saying go into business with people you trust and respect.
The corollary is to become someone who is trusted and respected by people who don't share the same skills and biases you have. Good places to start: seriously consider whether "the looks" have merit, and practice carrying friendly conversations.
I agree with your point, that a certain level of social skills is a must, although in my experience, when people start competing over making the best impression, many choices that improve it would be disadvantageous when it comes to execution.
The simplest example I could think of is typically being relaxed and simply agreeing with everything that your opponent says gives better surface impression than being focused on understanding your opponent and actually trying to defend your point (the classical salesperson vs engineer case). Except that approach would deadlock your execution, but nonetheless I see many people successfully using it to gain one's trust and get preferred over someone who pushed back too much.
I disagree. I've met a lot of super productive, obsessed people. Many are very nice. Though like Ben Horowitz put it, you have your peace time people and your wartime people. The ones you're describing might be wartime people, obsessed with making a company survive. A company like Google would want more peace time people. They're still damn good engineers but not so stoic.
