Great question Scott! I've got 2 printers at home, including a fairly new Canon mp490 dedicated photo printer, and I've been less than pleased with the results. I find that sharpness is retained with pics from my Canon 50D, but I have to pump up the brightness to get a print of anything resembling the original image. Problem is that eyes end up dark and some color/contrast is lost. I've tried looking through printer settings, calibrating both my laptop and desktop monitors, and I end up with the same results. Quite frustrating.
I got the Canon printer free after cashing in some airline miles that were soon to expire, so if I give up on it and sell it for a song, it won't break my heart at all. I'm likely to just go with something like mpix (Thanks Mike for the site info!) for the stuff I want to frame, and stick with Costco for my "bulk" prints. Been pretty happy with Costco prints overall, and their website is far and away easier to use than Ritz/Wolf.