You may be able to print at 10x17" with the output from a D70 (and I certainly have, with great results) but you can't do much cropping if you're targeting that size of output. Aside from the AF and physical build quality, the main different I noticed when I upgraded to a D200 was that I was suddenly free to crop aggressively and maintain high-DPI large-ish print quality.

That being said, there are still things I miss about the D70. It was smaller, lighter, and had noticeably better high-ISO noise characteristics. The latest batch of semi-pro to pro-level Nikons may have finally pushed the bar higher, but for a long time the entry-level 6MP bodies had by far the best high-ISO quality.

As far as glass is concerned, the 24mm f/2.8 and 35mm f/2 are both sweet lenses, too, and relatively inexpensive. I know that I found 50mm to be a bit long for many types of shooting, and a bit short for others, so I eventually settled on the 24mm and 85mm f/1.8 as my standard walkabout kit.