The D100 is an excellent camera. No doubt about it.
When it first came out it was $2,000 US as was Canon's D60 (which also was "still not there yet"). Now the D60 is out of production, and the D100 is available at B&H for $1,700 US.
The reason why I did not buy the D100 or the D60 was because I felt the price still was too high for the features they delivered. The Nikon is a good picture-taker, but you have to use RAW mode to get the resolution I wanted. Even the finest Jpeg setting is still a little soft.
On the other hand, the fine Jpeg mode on the 10D is almost indistinguishable to RAW in terms of resolution. RAW is fine for certain types of shoots, but Jpeg is much more convenient. I don't want to have to use RAW all the time to get a sharp picture.
The D100 and D60 also have a plastic bodies compared to the more robust magnesium chasis of the 10D. Again, nothing wrong with a modern plastic body, just not in a $1,700 camera.
There are a host of other little things that I'm sure Nikon will improve on their next release in this category, such as slow storing in compressed RAW mode, and the lack of a PC flash socket. None of this means that the D100 is anything less than an excellent camera. But for me, a photographer who needs every drop of performance for as low a price as possible, the 10D was the first digital SLR that hit the magic combination of performance and tolerable price.
I'm sure Nikon is working on their response to the 10D. And I'd bet it's going to be impressive.