Honestly dude, I did a ton of research before I bought my YFZ. Everything I read and everyone I talked to said the same thing....stock, off the show room floor the YFZ wins hands down. Every little thing I've done to mine has made it faster and faster. The new 08 suzuki 450's look pretty sick and are fuel injected, but I havent seen one run yet. If you do the "cam mod" (retard your exhaust cam one tooth for YZ450F timing) it makes a huge difference on the top end and pulls a lot harder. it's free, its easy, and if you have any mechanical knowledge at all it shouldnt take more than an hour.
Oh and I bought an '07 YFZ450 SE and love it!
any questions just ask