I sent them vibrant, highly saturated photos. They printed dull, lifeless, washed out photos with highly lacking contrast, color depth, and color saturation. Details also seemed to be blurred in the pictures. To say the prints are lack luster would be an understatement. Comparing them to my prints at other labs the difference was night and day.
After a useless back and forth email session with various customer service reps popping out of the woodwork (they have no phone number), I decided it wasn't worth wasting any more time trying. Even after sending several comparison snapshots that looked dramatically different from the originals, I was told they could see no difference, and to check the calibration on my monitor... Prints don't lie, and I have printed from many, many labs. None have been this poor.
In a crunch for time (I'd had my Mpix prints shipped 1 day delivery) I printed from a local drugstore... and got great results. I guess that's the silver lining of this horrendous experience. Now I'm debating whether or not to return the photos, as I'm guessing it will only amount to more hassle. Actually, I know it will be more hassle. They don't cover the cost of return shipping, and also don't accept returns on 4x6 prints. You still have to return them though if you want to get a refund on the rest of your prints and original shipping. Oh, but they offered me a 50 percent discount on color correction... oh joy.
In summation: lifeless and flat prints for some of the highest prices I've seen. Customer service did nothing but try to convince me that I was the one with the problem. Should have read some of the more recent reviews that talk about a decline in quality and saturation. I was lead to order based on the older more positive reviews. I will avoid this lab like the plague and would suggest the same to you.