Uh, hello? D300S! I would go for the D90. Performs better then the competing brands cameras in the same price range, with lots of features. Not to mention Nikon's superior High ISO performance, which is extremely important for low light shooting. Not all of Nikon's lenses are expensive, the AF-S ones are, but you get better, fast, quieter focusing with them, money well spent.
SheepStar
You know what sucks? I was about to post a counter post a couple days ago, stating that the high ISO of Nikon isn't any better than Canon, but after doing some research, it turns out you're right. Which is really a shame, Canon wore that crown for very long time, then they went high MP to please the uninformed masses instead of focusing on what really makes better photographs. IMHO, 3 MP is a lot less important than ISO performance, and even at ISO 800 performance, which isn't ultra high, it's not that quite up to par. And that's what I find lacking with my XT and would like to improve (That and a better viewfinder), but no, more MP is more important for Canon...
I have all Canon gear, but I have to say I somewhat despise Canon. Even today, I'd have trouble upgrading my ancient XT for a Canon DSLR, seems like every model is lackluster or too expensive. Seems to me like they're really about squeezing the most out of the lemon as they say; giving as little as they can for as much as they can. Nikon in contrast seems to try to release great cameras. And that's somewhat sad, that in 5 years Canon hasn't released a body which made me go: "Wow, I'd really like to get that!". Well ok, there was the 5D, but again, even today it's 2700$ and would require me to get full frame glass... Something I'd gladly do if the body was 1/2 the price, but no way I'd spend 4000$ for a camera and a zoom... Even lenses, price/performance it seems like Sigma/Tamron very often has Canon beaten, once again, Canon doesn't seem too interested in releasing good bang for the buck products. Just riding its customers base and releasing expensive lenses, very often really not too impressive imho...
For example, which f2.8 standard zoom does Canon have? One, and it's 1000$...
And image quality wise, it doesn't even leave Sigma's or Tamron's <500$ alternatives in the dust...