The difference between 1000D and 450D is quite marginal... You can read about it at DPReview.com. I believe most of the users here do not even use spot metering very often. The burst mode in 1000D is slower than 450D. However, most of the time, 3 fps is quite sufficient in wildlife, panoramic, building or simple action shots. The 7-point Auto focus point can easily cover what D40 or D60 could not, as they only have 3 AF points. My suggestion is that we invest in good, sharp and fast lenses. And hence when the body becomes obsolete, the lenses can remain useful a long long time. Lastly, I believe a photographer can still get excellent pictures, not from a so called scaled down camera, but from his skills, creativity and luck.
Happy shooting guys! See ya all tonight!
Regards