It's a weird situation. I like the place, but the hairs are up on the back of my neck that it's time to move on. Perhaps a little like you got at your uncle's joint?
I've achieved a number of the objectives I came into the company for. The team has now been operating pretty smoothly without much of my oversight. And you can see some of that result in that I've been spending a lot more time on the forums the past couple of weeks.

When that starts to happen, you start feeling a little redundant -- which is never a good thing given the bucks they're paying me.
And since I've had enough of you guys on these forums lately, of course...
The market is good right now for a change too. LinkedIn IPOed to some ridiculous valuation, which will feed the investor feeding frenzy and give me more options of my next project.
It also times well with some care for my wife's mother. My wife grew up as a single child of a single mom (her dad died of cancer when she was 3), and she's always had medical issues. This time she's going under the knife Monday to have a kidney removed as cancer surgery. More a catalyst than the reason, but...