There's arguably no single greater environment than learning from great people.

Communication, choosing your battles, patience, emotional intelligence, just to mention the managerial and partnership aspects. Too many technical / marketing skills to name.

I come from a 100% technical background, and I can tell the skills I've acquired in the past year will last me a long, long time.

Several, including pg and rtm. The hardest skill is knowing what could be simplified, and what's good enough.

Really looking forward to a reply here! Pg did write a bit about what he has learned from tlb: http://www.paulgraham.com/gh.html (see the "Recognition" paragraph)