Once in a while, its good to know if you want to shoot with the result of the pros, you jolly well use what they use....for a start. Composition skills, experience and ability to improvise and assess scene aside, at least you know you are getting there with the right lens.
I personally believe the Nikon D90 has identical capability as the Nikon D300 and with the right lens, we may well be seeing the summit of decent picture quality. Here's what the pros swear by each day