The worst thing about a PhD for me was the artificial size of it. A really good PhD is probably a natural series of ideas that spin off from a single theme - but in my case it was a single idea excessively dragged out. Smaller, quicker iteration on ideas is so much more satisfying and better for creativity.

I kind of hope that more people fill their 'do something creative' niche with startups in the future. Its more satisfying, not least because other people caring about what you do is essential for a startup.