If you would ask what's the single biggest advantage I've noticed since upgrading from my Nikon D40x to the D300s, I would have to say noise reduction. Obviously there are a ton of other advantages, but being able to shoot at higher ISO and then be able to USE the images is huge.
My D40x has an Auto-ISO feature, but I can tell you I NEVER used it. In my experience once I got above ISO 800 things started going downhill pretty quickly. When shooting this hockey game it would have been great to have a 70-200mm f/2.8. Not having one, however, I used my trusty 18-200mm, opened the aperture to f/5.6, set the minimum shutter speed to 1/1000th of a second, maximum ISO to 3200 and then let Auto-ISO handle the rest. Of the nearly 400 images I snapped, there were only one or two that ever fell below 1/1000th of a second.
Considering myself a long exposure landscape photographer, shooting at higher ISO settings isn't the norm for me. Having just put a little experience under my belt, however, I now feel much more comfortable letting things ride at higher ISO's when warranted. I've also yet to explore any additional software options out there for further tackling noise, but understand there are some that do an even better job than Lightroom.
Do you use any additional noise reduction tools in your post processing? Which one(s) would you recommend?