Sure, I am
Actually, I would answer in the negative.
Some of the skills, as you say, are the same and can work for both GM and writer. And yes, of course there are differences - but those do not make the difference.
There is a difference between verbal and written description, for example - I for one give reasonable written descriptions, but quite poor verbal descriptions

(). This I find to be a major hurdle as a GM. Well, that and lack of time

But it is not a show-stopper.
There are other differences of course, but I ain't gonna do a list. I suggest you won't find a difference that really is a show-stopper.
See, I think the essential skill of being a DM is empathy to what the players want, and being willing to deliver it. If you do that, then even if your plots are mediocre and your descriptions are so-so and your roleplaying non-existant - you could still orchestrate a good game. (Of course, I mean catering to their real wants, not giving them perks like magic items or whatnot but rather setting up intrigue with the family of one PC, providing some plain hack-and-slash for another player, and so on.)
In contrast the primary skill of being a writer is being able to construct made-up constructs others can relate to (characters, descriptions, and so on that will evoke the reader's emotions); it helps if there is a good plot structure too. This is a key asset to a GM, but I actually think it is secondary. Anyone has it to some degree; the empathy to the other's needs and willingness to commit time and effort is much more rare in my mind. Once those are given, the GM will improve his skills with time - but without them, all the skills he would gain will be in vain.
So some of the skills of a writer will help you build better adventures, run them more evocably, and generally be a
better GM. But being good or bad to begin with - that, I find, has little to do with writing skills.