Aloha,
But on the other hand, from a VCenter standpoint - 5.1 is a completely different beast. Looking at the posts in the VCenter Community, you'll see quite a few people having very significant problems. And several people are downright irritated.
I was in your shoes not long ago. In the end, I took the path of least resistance and went with Update 2 and never looked back. I know that at some point I'll need to go beyond 5.0. I am hoping by then VMWare can clean up things a bit.
Bill