I have dual screen here and I do mostly play games in Windowed mode instead of fullscreen because most of the time it allows me to watch, change music on my other screen or more importantly reading articles, forums and etc.
I'm on trial with Action for 2 days now, it seems like Action is 50/50 works on Windowed mode games. I know in fullscreen it will detect the DX fully.
Game now I am having 50/50 chance to have Action work is Guild Wars 2.
I am coming from Dxtory, and the reason I'm coming here is to look for a better light weight encoding that doesn't eat my whole HDD and the bonus is that those files from Action is editable in Premiere Pro unlike Dxtory + x264vfw = uneditable means I have to convert to RAW with 30-50GB files before importing to PPro. Action can allow me to have 3-4GB files and it can be edited. It's very sweet to have.