I use Shutterfly to make calendars, and I also turn off the Auto Exposure for each photo. The one time I did not turn it off, my images printed darker than expected.
I make a lot of photobooks and have used Mixbook exclusively for photobooks for the last several years. They offer a similar user interface as Shutterfly with pretty much the same features. I use an old Dell computer with a Dell monitor. I have to say that the print quality of the photos is pretty much identical to what I see on the screen. I know that what I see on the screen (good or bad) will be what I get. I am happy to know that what I see will be what gets printed.
Mixbook does have a warning if you zoom up a picture too much and the resolution gets too low to print well. I think maybe Shutterfly does the same thing, but I can't remember for sure.
There are options in Mixbook for different paper qualitys, finishes, and of course book sizes. I do hardback books with the standard paper. I believe the maximum page size per book is 400 pages. I have made several hardback books about 125 pages in size. I have been happy with each one. They always have a promo going, and I wait to order until one gives me the best deal. Recently, a 125 page, hardback book on standard paper cost me about $150. Not cheap, but happy results.
I do edit many of my images in Photoshop a little bit before uploading them. Usually just some basic brightness/contrast toning and a little bit of unsharp masking (sharpening).
One time, a book was damaged in shipping, and Mixbook reprinted it, no charge. One other time they had trimmed some pages weird before assembling it into the book and some pages were mispositioned. They also reprinted that for free. I have been happy with their customer service.