Nearly always from the ground...unless I have a good spot to set up and leave my ladder stand.
I started hunting on the ground my senior year of highschool when I dislocated my scholder. The doc said it would be ok to shoot a bow, but to not do any pulling from over my head. So I was grounded for the season and ended up killing a decent buck at only 8 yards.
I always thought treestands were a bit of a pain - especially climbers before daylight. Now I just open up my fold-up stool and sit somewhere with good cover behind me to break up my outline. I have yet to have a deer bust me trying to draw while on the ground. I just blew a shot at a doe this past Friday (pick a spot is something to remember) and even after I missed she still had no idea I was there, but just didn't give me another shot.
If I start getting busted drawing on deer I might think of going back to a treestand more often, but right now a new treestand is at the bottom of my wish list.