Upgraded from a D50, so its quite an upgrade really, got my D50 in 2006.
Haven't played with it too much yet but so far its rather good, focusing is much quicker even with my Sigma 105mm which I did find slow on my D50 not so on this, same with my 50mm F1.8. Wouldn't mind trying my 70-300 on this either, that used to hunt and generally be slow so hopefully it'll be an improvement but a friends got it at the mo.
The AI indexing tab is rather handy as well as it can read the aperture from my 400mm F5.6 which means I can use it in Aperture priority mode.
Auto-ISO is great, set a minimum shutter speed and a max ISO and it'll up the ISO until it gets the shutter speed and if it can't then it'll max the ISO and drop the shutter speed.
File sizes could be an issue before long, 50 pics was about a gig might be out of hard drive space soon
It does weight quite a bit more and it'll take a bit of getting used to 2 command dials.
Overall very pleased with it, just need to get some proper pictures taken with it.
Oh and £180 of vouchers and £36 worth of quidco is very handy!