I've submitted manuscripts to both Deseret Book and Shadow Mountain - one to each, if I remember right - and been rejected both times. At least we can say they're not taking just everyone who wanders in off the street
I've also spoken to one of their editors on the phone. My mother accosted her on the bus one day (my mom doesn't know a lot about the publishing industry, but she knows enough to be able to tell this woman was reading a manuscript), and she expressed interest in speaking with me when she found out I was a writer with a manuscript requested by multiple agents. We spoke for about half an hour, and I found her to be kind and knowledgeable. The last thing she said to me was, "Well, now you know at editor at Deseret Book, so feel free to get in touch!"
As several others have mentioned, Shadow Mountain published Brandon Mull's Fablehaven series, and Ally Condie, author of MATCHED and CROSSED, published multiple novels with both Deseret Book and Shadow Mountain before seeking an agent. Shadow Mountain in particular seems to specialize in MG fantasy and sci-fi, so if you have a manuscript that fits either of those genres, I wouldn't hesitate to submit it to them.