I've come to the same conclusion. Nikon certainly will come out with replacements that are better, but I think I would enjoy the D100's capabilities now. I've put one on hold at a local photo shop.
What drove me to do this? I think the realtime feedback on composition and exposure would be a plus for me. I'm a pretty decent photographer, but the lag time to get slides or prints back slows down the learning process. In addition, I'm scanning a lot of my work these days, and the D100 will shorten that time. Finally, it would be fun to have for family photos, etc. where it's nice to have quick results.
Hesitations? I still like shooting slides for projection, so I may be forced to take two bodies where I previously only took one.