I used Costco's printing services for the first time last week and was amazed by the prints. I normally used Walgreens (I know they suck, but for small wall collage stuff it worked), I had used Shutterfly one time (had 101 free 4x6's). I wanted to do a collage of my best landscapes in our living room, I started by pricing out Walgreens 11x14's but there was no way I was gonna be able to print everything I wanted at their price ($9.99). I then priced out Mpix and Bay, both were much better in pricing with good shipping options. However someone said I should check out Costco first. At $2.99 for a 11x14 I figured I could not go wrong.
So my order consisted of 26 prints ranging from 5x7 to 20x30 (was only $9.99). My total was only $65.00 for the entire order and was ready the next day.
Got them home and was amazed by the quality even of the 20x30. I shoot with a T3 and kit lens so I was not sure how something this large would turn out. And all the others looked so much better in the larger sizes compared to some of the smaller copies I had made in the past. I edit on a laptop with no calibration, I check off the color correct box when uploading as well.
All I can say is if you have a Costco near by and have not tried them your missing out. It has opened a whole new world of printing for me.