$1000 is ok as long as you know that you're getting what you want. I got the premium and sport packages ($5000) for my car just to make sure that I had the best.
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Of course, not having to pay a dime make the decision much easier.
I just don't think an extra grand is worth it. It would be if the D300 blew the 40D out of the water in every department. The D300 has a few advantages, but it is significantly slower than the 40D, which makes some of its extra features not as useful. What's the sense of having 50some autofocus points if it takes twice as long to focus on anything? It also doesn't shoot as fast as the 40D. It appears to be better at high ISOs and have slightly better colors, but those things can be corrected in Photoshop. I dunno, for all of its strengths, paying 1k more for a slower camera is just eh.