Seems like its worked pretty well for him. He's 8-2. And the entry he used in his loss was a very unusual one, certainly not his normal entries. It is an entry I've seen demonstrated often, but rarely used in competition. The fact that it didn't work isn't an indictment on spinning or rolling leg attacks anymore the failure of Harold Howard's front flip into a kick is an indictment on the efficacy of kicks. It is essentially a version of the technique at 1:53 that he is using:
Not saying that technique would never work; I've used variations on it, but it is a more obscure, less common technique and like I said, the fact that Hall didn't pull it off in his fight doesn't somehow discredit the whole endeavor of rolling for the legs somehow.