It seems like as iTunes is extended to manage all media instead of just music, it's going the same way QuickTime Player went 5-8 years ago (I forget exactly). Back when QuickTime 4 came out, Apple created brushed metal, which was completely non-standard and unprecedented. The entire QuickTime Player interface was a hacky and out of place.
That was in OS 8, though. In OS X, non-standard interfaces are not only precedented, they're pretty much the norm. See Dashboard. And iTunes 5-6.
Again, it looks like Apple wants to make their multimedia center look like a physical multimedia center instead of a regular program. Brushed metal doesn't cut it anymore, since they've bastardized it to the degree where it's used for web browsers, calculators, and just about everything under the sun. The non-standard interface has become standard, so they're making a NEW non-standard interface.
And the new non-standard interface will probably become standard in time, too.
My reaction to iTunes 7 is unusual. My first impression was good, but the more I use it, the less I like it. I really do hate inconsistency. But I guess I've become desensitized to it when it comes to iTunes. I think only iTunes 4 used a completely standard appearance (and even if was slightly different, due to its Carbon nature).
Also, I see iTunes 7 as being a step towards Leopard and Apple's new design philosophy. Apple has been dropping conventional interfaces gradually for years, and Leopard seems to take that one step further with bizarre, high-animation interfaces like Time Machine. iTunes 7 seems to be in line with that philosophy, along with Front Row. I'm not sure if that's a good thing or a bad thing, really, but I do think there's some level of consistency in the move, and I appreciate that.