Comparing Nikon D300 with Canon EOS 40D
Resolution (MP): 10.1 v 12.3 (Nikon)
Sensor size: 22.2x14.8 v 23.6x15.8 (Nikon)
ISO: 100-3200 v 100-3200 (draw)
LCD viewer: 7.5cm v 7.5cm (poss. higher resolution on Nikon?)
AF points: 9 v 51 (err...Nikon?)
Burst: 6.5fps (70 shots max.) v 6fps or 8fps w/ battery grip or AC power (draw)
Viewfinder: 95% coverage v 100% coverage (Nikon)
Weight: 740g v 825g (Canon)
Availibility: Any time now v November (Canon)
We don't know what the price difference is going to be in Aus, yet (it doesn't always translate directly from US prices), but it's obvious that the Nikon is the better spec'd camera. That's not to say that the Canon is a bad camera, of course, and the Nikon is quite heavy in comparison. The 40D would be a good option if you want to save a few $$, aren't a weightlifter in your spare time and don't need 51-point AF. If you want the best camera in the mid- to high-prosumer range and you don't mind paying a bit more for it, the D300 is the way to go.
Australian prices for Nikon D300 will be available in October...delivery in November, according to Nikon. Canon 40D will be available from next week (early Sept.), hopefully, in body only and with 17-85mm IS lens [enthusiast] kit form.