Before buying a Canon 400D it is very important for you to actually physically handle and work it bit with the 400D. To me, the grip is far too pinched and way too small. I don't ever feel that I have a good grip on the camera. It also does not have any IS, which is a great feature to have.
I use spot metering a good deal, so for me when you add the lack of IS, the lack of spot metering, and the really poor ergonomics together. I would not touch the Canon 400D.
A better deal would be the Pentax K100D which has spot metering, a great grip and IS. It is only 6mp just like the Nikon D-50, but the difference between the 8mp of the Canon 400D and the 6mp of the Pentax K100D is not that great. With the Pentax K100D every lens you ever put on the camera has IS, because the IS is built around the imager and no you don't have to pay high prices for Canon's very expensive IS equipped lenses.
It is your decision, enjoy the buying process.