Herbert is well liked, even though he really hasn't put much of a footprint on the state's politics, he usually leaves everything to the legislature, which is a bit less popular than he is. He's basically an affable grandpa, even if I think he's a corrupt sleazebag who deserves little credit for our economic recovery.
You could arguably say that about about both of the Governors who preceded him, not counting lovable old Olene Walker.
I think Huntsman is overrated (and more far-right than he's portrayed to be), but not quite corrupt, and I don't recall much about Leavitt. Herbert is the one I have the most familarity with, and he's actually had several corruption scandals which seem to slide off him like Teflon. His "Available Jones" thing, the UDOT scandal, his big donations from agriculture which coincided with an infamous "ag-gag" law... and he and half the Republican leadership in the state (including the current AG) have gotten donations from a secretive polygamist group known as the Kingstons.
Herbert's an affable "good old boy" and nothing the Utah Democrats throw at him (or any other GOP governor for that matter) seem to hurt them.