I just switched from a Dimage 7i to the 10D. I got the 10D with the very popular 28-135 IS USM lens and the 100-400 L IS USM back breaker. As you probably know, the 10D esseentially multiplies the focal length of any lens by a factor of 1.6x. So, the 28-135 zoom is really a 45-216 when on the front of a 10D, giving a farily similar range to the Dimage 7i for about $400.
If you're going to buy the 10D, you should probably get at least one nice Canon lens to go with it. As for lenses in the $1000+ category, I really must say that I'm blown away by my "L" but still think the 28-135 represents a good 10D starter lens that won't break the bank. Another benefit of buying a Canon lens with your Canon body is that there is no excuse that the store or Canon can give you if the two don't work together perfectly.
One thing I learned from my first day with the 10D (actually, the first day with my Dimage 7i as well): the first charge of the battery won't last very long. Don't panic. After a few charges I've now been going several hundred shots even with the image stabilizer.