Hi Wildboy,
I hear where you are coming from, as I have love/hate relationship with my D3000.
For sport I hit the limits of the D3000 constantly, both ISO-wise & the fps/buffer performance.
For landscape, I find lack of mirror-up annoying, and live view would be handy sometimes, but the main limitation was my kit lens.
Before you get a better body, keep in mind that quality lenses will push out the body limits further than you think.
I picked up second hand a Nikon 80-200/2.8 and Sigma 14mm/2.8, and have got better shots than I thought possible out of the D3000 body.
Lack of motor drive can be a pain, but it sure improves your manual focus techniques!
I suggest you follow Thom Hogan's advice, which is along the lines of that already offered above by the others.
Start with yourself & your technique, then consider better lenses before you look at a new body.
http://www.bythom.com/blame.htm
Keep practicing your skills. Here a couple of samples of what you can do with a D3000 with a decent lens
Midnight Blues
Stone Maidens