We have dined at the GM twice in the past three years and wasn't impressed either time. As others have said the wait staff were not necessarily unfriendly, but rather disinterested and appeared to have other things on their mind despite our being the only diners in the restaurant.
We ordered three dishes, one satisfactory, one very bland and one that had an odd flavor, ... what I imagine floor cleaner to taste like. At the end of the meal the third dish was cleared relatively untouched with no inquiry from the server, which I thought was odd. Our intentions were to share everything so 2 of 3 wasn't a big deal.
In all it wasn't a negative experience, but not memorable either. Meh, sums it up nicely.