I have a 15 inch MBP I bought in 2007 and it's still a much better machine than most of the Windows laptops I see at Best Buy. And it still makes me very happy. After recently getting to play with the new unibody model, I think they're great machines, but I don't feel any urge to buy one. For me though, it has nothing to do with the black keyboard.
Pros: The new design is sturdier and the cpu/graphics/ram/etc is faster. It also supports (more) multitouch on the trackpad.
Cons: There are two and both relate to display issues: miniDisplayPort and gloss.
I'm sure you can find plenty of posts on these boards sharing exasperation over the choice to go with only glossy screens and not offer a matte option at all. Not only is the only option glossy, but it's more glossy than the old glossy option. I don't mind glossy for home use and it makes movies look beautiful, but for people using it in an office setting or outdoors, it's not a good idea.
For me personally the biggest con is losing DVI output. I hook my laptop up to monitors, projectors and my TV all the time and DVI is the best option for compatiblity. The only external monitor you can use without an adapter is Apple's own new 24 inch.
They no longer provide adapters like they used to for their mini-DVI on the MB, so when you're looking at the cost of the new machines, figure in the price of at least two adapters, one for VGA and one for DVI, and if you have a 30-inch monitor, you'll have to pay for the $100 DVI-D adapter. You'll even need an adapter if you have one of the few monitors that supports ordinary DisplayPort.
Even that wouldn't be so bad except they've now enabled HDCP so forget about watching DRM'd HD content you buy on a TV or any external monitor except Apple's new 24-inch one because the adapter will make it an "non-trusted" connection. In other words, they are penalizing people who pay for movies and effectively rewarding people who pirate them.
Anyone who had an old Apple Cinema Display with their own proprietary connector can tell you the heart-ache of Apple-only connections. In my office, every time we upgrade a computer we have to buy a new monitor even though the old monitors still work wonderfully, simply because they used Apple's proprietary connector that Apple no longer supports and the adapter is nearly as expensive as a new monitor.
I think Apple made a big mistake in using with miniDisplayPort regardless of whatever technical or size advantages it may have. The sad thing is, most of us will buy an Apple anyway when we need our next computer no matter how disgruntled we are. But I personally will postpone that day as long as I can and keep an old laptop with DVI. If other manufacturers adopt Apple's "standard" or the company switches back to a real standard, I will reconsider. Until then, I'm happy with my machine.