[*]Consumer DSLR owner that's upgrading (D40, D40x, D50, D60, D70, D70s, D80, D90, D3000). For all but the D90 user it's a no-brainer: if you need or want more, the D7000 is a lot more. It's a bit like trading in your old CRT-based TV for a nice new LED backlit LCD HD large screen one. There will be some learning curve shock, but the performance you can obtain puts you in a different league. D90 users aren't making so large a step, but it's still a significant step. If you're comfortable with 12mp and ISO 1600 tops, stay with the D90. If you need to shoot in low light, need more pixels, or feel disadvantaged in autofocus, the D7000 is a step up for the D90 user.
[*]Prosumer DSLR owner (D100, D200, D300 user). Here's the category that's the most troublesome. D100 users, well, step right up. D200 users should take a long close look. D300 users? Well, there's the rub. You'll give up a little, you'll gain a little. So, no, unless they need a DX backup body I don't think the average D300 user is going to be interested in the D7000. Really. I mean that. The thing that'll annoy you about the D7000 is the buffer, and that's a bigger annoyance for the serious shooter than ISO 3200 on the D300. On the other hand, if you're buying from scratch and considering either a D7000 or D300s, then things are a little different. You have to figure out which of the things that are different between the two cameras is more important to you. Then if you're smart, you'll save a few dollars and buy the D7000 ;~). But if you're a raw shooter who's at max frame rates all the time, make sure you're happy with the buffer (I doubt you will be).