I use dried grass in my run and LOVE it. It makes a soft bedding (good for heavy breeds), is clean, and smells nice. The chickens love scratching around for bugs and seeds, which keeps it turned and fluffed up. I have no problems with odor or flies.
Personally, I prefer organic bedding to sand, but that's just my opinion. I like knowing that it I can easily remove everything down to the 'floor' - and replace when necessary. Used grass gets added to the compost bin (chicken poop and all). Best of all it's free. The lawn mower chops it up and bags it for me, and all I do is dump it on the carport to dry. I have to mow the lawn anyway and the clippings were already headed to the compost bin. Now they just make an extra stop to pick up some poop, lol!
I do have one small spot that has coarse sand (design flaw - sand was a quick fix), but it is a very thin layer. Even though I don't like the sand, right now I'm leaving it because they prefer to lounge in that spot - I'm guessing because it's cooler (we hit 97 yesterday). I keep trying to put grass there and they keep kicking it out, lol! So for the summer I'll keep it sand, but in winter I'll pile the grass in there as well.