To be quite honest, I've actually used both stall and offensive teams for about equal amounts of time throughout my battling career on the UU ladder, but I've been leaning towards using offensive teams more, experimenting with both balanced and spike-stacking offense.
It is my opinion that the current metagame makes stall less effective than it has been in the past, being completely obliterated by Swords Dance Gallade (among other things) without much trouble. Additionally, the fast paced metagame UU seems to be leaning towards now probably won't even give stall teams much of a chance to set up. Note that, of course, I may be mistaken in my beliefs as I probably haven't battled as much in the current stage of the UU ladder as compared to the other people here.
It is my opinion that the current metagame makes stall less effective than it has been in the past, being completely obliterated by Swords Dance Gallade (among other things) without much trouble. Additionally, the fast paced metagame UU seems to be leaning towards now probably won't even give stall teams much of a chance to set up. Note that, of course, I may be mistaken in my beliefs as I probably haven't battled as much in the current stage of the UU ladder as compared to the other people here.