I had a bunch done when they had 50 free prints + 50 for a penny each plus a free 8x10. The grand total for 100 4x6s and the 8x10 was, oh, $7 or so. If that's too much, I could have picked them up from a local Walgreens and gotten free shipping, so the grand total would have been 50 cents plus tax. However, I wanted matte rather than glossy, and that's not available locally.
I'm pretty satisfied with the results. I did find the user interface a little bit of a pain to upload full-size photos - by default, it has you upload low-resolution shots.
I'll certainly use them in the future for 4x6s especially during the sales - I actually just missed another 50-for-1c-each deal. For 8x10s, there's another site (begins with an M, can't remember the name) that's more high-end and has cheaper 8x10s.