As you first begin experimenting with the Twitcher, you may think it isn’t as fast as Windows‘ Alt+Tab. This is because it does so much more, and gives you options between cycling through just the windows in the current workspace or all windows. If all you really want to do is toggle quickly back and forth between two apps, make sure those two apps are in the current workspace, and minimize all apps and/or windows besides those two. Now a quick tap on Ctrl+Tab will move you quickly between those two windows, ignoring everything else for lightning-fast window switching.
Bonus: Most applications will let you switch between open windows via Ctrl+Opt+Tab (Opt is the Win key for most users). To make this work, you must tap the Tab quickly — if you hold it down you’ll get the Twitcher as usual.