Were just there last week for a delicious lunch and have to say, this is an underrated restaurant. Here's why.
The food is not so different than the Liberty Tree Tavern - family style platters of flank steak, catfish, turkey, potatoes, very freshly sauteed veggies (all at table agreed that everything was delicious). The character greets are numerous and convenient -- they come around the inner and outer circle and there's no confusion or worry that they won't. The place is a comfortable and restful sit-down of sanity in a now very busy Land pavillion.
But Epcot and, specifically the World Showcase, bubbles over with a variety of interesting and enjoyable restaurant alternatives. So GGrill sometimes gets overlooked. If this place was in TomorrowLand, you couldn't get an ADR. The day we went (the Land was packed), it was 2/3rd's empty.
Possibly the wonderful refurbishment of the Seasons Marketplace (or whatever it's now called) downstairs has had a negative affect as well. But we thought the Garden Grill was a fantastic dining experience.