The most overrated element in Mitt Romney's big Florida win? Has to be his new debate coach. Sure, you can make an interesting story of the fact that Romney had access to the best that the conservative network has to offer. Indeed, you could talk about how former Liberty U. coach Brett O'Donnell's willingness to work for the Mittster is a good example of how Romney won the nomination: basically, he managed to dominate moderate conservatives while being competitive among social conservative, Tea Partiers, and other more extreme groups. The specific effects O'Donnell may have had on Romney's rhetoric are interesting, too.
However. As far as actual coaching is concerned, Romney was widely seen as the best debater among Republicans right up through the New Hampshire primary; a lot of the debate reviews, especially in the fall, were along the lines of "well, Romney of course was the best, but let's find something else to write about because it's boring to keep pointing out how much better he is at this than the rest of the field." The one thing that Romney seemed to really have problems with -- and here I'm very much agreeing with what I think was the conventional wisdom -- was talking about his wealth. And in my view, at least, that didn't change in the Florida debates.
Remember, one of the reasons people think that Romney got to the point he was at in the GOP race is through crushing his most serious opponents, Tim Pawlenty and Rick Perry, in debates. I don't know whether O'Donnell helped Romney on the margins or not, but the idea that his coaching was a major factor in Florida seems extremely far-fetched to me.