I think that the Canon and Nikon ranges are still not exactly lined-up. The D90 fits somewhere between the Canon TI1 and the Canon 50D. I would compare the Nikon D5000 with the Canon TI1.

Some D90 features that the TI1 doesn't have:

- more solid body, bigger, better to hold with large lenses
- much better viewfinder (real pentaprism)
- same control layout as the pro DSLR's (two knurled wheels to control shutter speed and aperture)