gof: I've printed a LOT of digital pictures at a LOT of different places. My unscientific review found that the best quality, by far, came from Ofoto. But they are also, by far, the most expensive, even when they have coupons.
Kodak's Picture Center is cheaper, especially when you go through a "partner" like Costco (which offers 25% off). However, even though Kodak now owns Ofoto, they are still processing digital prints separately, and on different paper. The Picture Center prints tend to be much more washed out than the Ofoto prints.
I've had pretty great luck with Wal-Mart B&M printing, and (at least the store I go to) can take pictures in just about any format: Smart Media, CF, floppy, CD. I'd place the quality somewhere between Ofoto and Picture Center. I generally use this option only when I'm in a hurry.
So, for me, Ofoto is still the best. It can get really expensive, though, so I tend to use them primarily for high-quality enlargements or when I'm creating a gift for someone.