The only con for us is really a pro also. If you stay at a mt Vernon property, you're on your own. We were long time sonesta maho people but now have fallen in love with mt. Vernon.
We spend Christmas and New Years there and the weather is perfect. Last trip we didn't even rent a car--took a cab to Marigot one day but that's it. It's a nice walk to club orient where you can rent chairs and enjoy (imho) the best of orient beach.
There's a pizza shop at mt Vernon that delivers to your room.

The road to mt. Vernon has been in "terrible" shape for a long time. I think it's a perpetually inevitable condition.