I went to the 7D from a 40D. While the 40D was a big jump up from my earlier Canon DSLR, there were things I didn't like:the rear screen was so grainy I had to zoom to check focus. It over-reported over-exposure highlights. It would hunt for focus in low light.
The 7D screen in triple the dots, and I can instantly tell if focus is on. The focus is fast, with none of the hunting I had with the 40D. Battery life is superior. So much so I'm using the 7D without a dual-battery grip, which I had considered essential on earlier bodies. It is better weather-sealed. So far I haven't had it fog up, a problem I'd encountered several times with the 40D.
What Canon basically did is put a whole lot of 1D features into a 1.6 crop body, and sold it for the price step above the Rebel line.
Noise? OK, there's noise, but remember, we're shooting 18mP at ISO 6400. For that, I'll be happy to wait for raw converters and noise ninja to catch up.