I bought Jack's first album because I liked what I heard on the radio. But my friends who have a music education were not impressed. They'd shake their heads and tell me "it's not good." I don't know if it's because of what they said or my own instincts, but I gradually stop listening to Jack.
As for Jason Mraz, on the other hand, my friends (who have a musical education) are very impressed with him. My sister and her husband (who is a talented drummer), think he's brilliant.
check out Ray Lamontagne if you want some smarter music than either of these guys, totally original and one of a kind voice, he's awesome live too.