The only Yamaha 4 stroke that I have ever rode was a 2004 YZF450 and I wasn't impressed at all. My 2005 CRF would turn circles around it and was easier to ride. Unless they have come a long way in the last 5 years I'll stick with my Honda.
Apparently it is one of the best 450's ever made (2011 model)
A couple reviews and one at DR saying it was their favourite 450 ever. I still don't agree with FI though, i like to stick with my Keihins with FI too many things can go wrong, with a carb only thing that can go wrong is your jets but then again itll still run.