I personally disagree with all the bashing his artwork gets. I love it because it is different than everyone else. It was his creation, Cable, that drew me into the X-Men books. Think about it this way, he has to have fans for Toy Biz to make a subline of XForce toys in their XMen line in the 90's.
Cable, Shatterstar, Deadpool, Stryfe, Domino. RL created some great characters.
As for his leaving DC? I've read several interviews/reports of his interviews. It seems to me that many of his reasons are the same ones George Perez gave for leaving as well.
You are right that Rob has the ability to create characters out of seemingly nothing. But he has become very formulaic in the way that he is doing it. What worked then, won't automatically work now and he doesn't seem to care.
The problem I have with Rob's art is that his anatomy is beyond broken.
And I have no problem with him leaving DC. I have no problem with the reasons he is giving for leaving either. The problem I have is in the way that he is mouthing off and presenting himself. If he had even a modicum of composure or professionalism I could let this slide.