Recent quotes:

Why Angel Investors Don’t Make Money … And Advice For People Who Are Going To Become Angels Anyway | TechCrunch

If the average VC fund barely makes money, and seed investments represent even less compelling opportunities than the ones pursued by venture capital firms, then the typical return for angels must be atrocious. Even Ron Conway’s second angel fund, which had the good fortune to invest in Google (a 400x cost winner), only broke even (that means close to a 0 percent IRR)!
Given two people of approximately the same ability and one person who works ten percent more than the other, the latter will more than twice outproduce the former. The more you know, the more you learn; the more you learn, the more you can do; the more you can do, the more the opportunity - it is very much like compound interest. […]Given two people with exactly the same ability, the one person who manages day in and day out to get in one more hour of thinking will be tremendously more productive over a lifetime. […]You have to neglect things if you intend to get what you want done. There's no question about this.