I think the Texans have lived through Smith's growing pains as a rookie GM. Whether directly attributable to him or not, he has been the GM to navigate a nearly perfect first round success rate. I do think he knows a thing or two when it comes to scouting defensive backs, too.
I doubt the early-years version of Smith could have pulled off (or had the guts to pull off) the big trade up for Watson. Of course, he probably has considerably more confidence from the ownership team to make such a move now, too. So there's some benefit then to having tenure from the GM role.
Heck, it says a lot when another team in the division sees better results from an orangutan making picks over their last GM.