I've tried several other apps like this, and after paying for a different one discovered that Witch is more mature and has a better feature set. I have had problems intermittently with lag for command-tab switching, but after upgrading to Sierra (which required the painful switch away from Karabiner to Karabiner Elements) and then some changes to my Karabiner-Elements setup suggest that one of my Karabiner-Elements configs might have been at fault for the lag. I'll adjust my rating down if it turns out that Witch itself is to blame. But the feature set is really top-notch. I'm hoping that its performance is equivalent.
The only reason I didn't try Witch before the competitors is that I tried it MANY years ago when it only (AFAIK) did Windows-style switching, which switches windows instead of apps. While I can understand a former Windows user wanting that, I find Apple's app-oriented switching to be superior 95% of the time for my style of working. Fortunately Witch now lets you do both, and also a combination, where you can first switch between apps, and then (without opening a different switcher UI) drill down into the windows for the chosen app. This is the best of both worlds. It is also HIGHLY configurable.
There are some features I would like it to have, but nothing else (AFAIK) has them. It would be awesome if we could write functions (shell or AppleScript) to determine if an app is shown or hidden from the command-tab switching menu. This would allow much more sophisticated control over that.
It would also be nice if we could explicitly hide an app from the switcher in the current workspace, using (e.g.) shift-control-H. This would allow ad-hoc changes to which apps we want to show and hide, and wouldn't require OS hiding to result in Witch switcher hiding, because I never find that the two are the same for me.
Some people have complained about the price. HUUUHHHHHH? It's very cheap! Developers need to eat and pay rent! It might seem "simple" because it serves a very well-defined need, but an app like this is actually a very impressive feat. I'm glad to pay for it.
My only serious concern is the performance issue. If that returns, and cannot be attributed to something else, then I'll drop the stars WAY down. If you see this remain at 5 stars, then I recommend this over all the others like it.