The photo quality was high (at least for the 3.3 megapixel wonders my repeatedly broken camera kicks out. Your mileage may vary.) As far as the service goes, the web site was easy and trouble-free, and the prices seemed reasonable ($0.49 for 4x6's, $0.99 for 5x7's, and $3.99 for the 8x10). They also have wallet sizes, frames, cards, and other options. The picture arrived in the mail speedily. And the web site is full of nice features: It's easy to keep a list of recipients to send the folks back home pictures. Of course, like other sites, you can share your pics online and have the folks back home order them themselves. And they even have an (optional) downloadable helper app to make uploading multiple pictures less tedious. (I haven't tested that yet, though.)
A usage note: Since none of the traditional picture sizes are the same 4x3 aspect ratio that most digital cameras take, your photos will be cropped if you just upload them as is. If you care how your photos are framed, I recommend cropping them to the proper aspect ratio for the size of print you're ordering yourself before you upload them. Or, even handier if you're ordering multiple sizes (which have different ratios), you can use their cropping tool (you have to dig for it, though). I point this perhaps obvious point out, because it didn't occur to me at first, and my 8x10 is not cropped as I would have chosen it to be.
I know Shutterfly has a few competitors. I haven't tried any of them out. Let me know if you know better than I.