Hed be a definite upgrade over Butch, but Mullen has baggage.  
I do think I have a little inside knowledge on Mullen from his time at Florida:
Mullen does not play well with others, as in colleagues in other sports, Administrations, etc. He is notoriously jerky, former UF AD Jeremy Foley was not a fan of Mullen at all.  Foley never even looked his way for two openings at UF.  
Hes an average recruiter, and that goes back to that sorta standoffish personality not playing well in living rooms.  
Lastly, and maybe this is least relevant or important, but there have been rumors for years that Mullen is an atheist.  I heard this when he was at Florida because as everyone knows, Tim Tebow is a devout Christian, yet the two worked well together, putting aside religious persuasions.  Mullen has never publicly knocked down these reports/rumors. Ive heard other reports that hes a Scientologist, which I guess is a less harsh way of saying he believes in a Supreme Being, just not Jesus Christ.  
Of course, a lot of this stuff was fanned and flamed by Ole Miss fans over the years and used against MSU in recruiting.  I do not have definite proof its true and to each his own with regard to religion, but its interesting that he has never attempted to clear up these persistent rumors through the years.  And of course, with political correctness among the media, I dont know if hes ever been publicly asked.  
I guess my point is, this is the SEC, Christian-dominated geography.  Im not sure hes a good fit for UT or UF.