When I was just starting out, I always thought that this or that company was "better" than my current situation. What I have learned over is this: "The Grass is
NOT Greener on the Other Side". In most cases, it is what you make of your current situation. It is a hard lesson to learn and there are cases where moving to a "New" situation is truly better. My suggestion would be to exam what you have and see if you can make it better first and then consider moving on.
I wrote this because I
read this on Techcrunch about why some ex-Googlers left the Googleplex. Hey - the reality is that Google is a company - pure and simple. And as the company grows it will by nature be like any other big company. Big is not always better and Google is pretty big now. Perhaps they should think about breaking up the company a bit - into many smaller companies / independent divisions.