After browsing a few of the replies here, I felt it necessary to say a few things;
First of all, I am still trying to like this app. It's like every time I add the license info, Overflow 'forgets' that it is unlocked after a restart. Frustrating. It's giving me a time limit now and I'm not sure that I will like it before that time runs out. You may think I'm being harsh, but I have put a lot of time and effort into giving this app a fair chance.
Combining the license issues and the fact that I've bought both DragtThing (way better implementation of the same idea) and PathFinder (has an Applications button in it that lists the contents of /Appliations, as well as via the PF menu icon) I just don't see the use for this. If others love it, then great.
You can't argue with free, but when I was looking for a UI element that this might have filled, I tried Butler, LaunchBar, DragThing, and Quicksilver. If this were available (or advertised better? I found all the rest on MacUpdate with no prior knowledge of any of those programs) I definitely would have tried the demo and chosen any of the above over this.
I use QuickSilver heavily to launch programs instead of dock or menus. I'm just a more keyboard-centric person, and it feels like Overflow is very decidedly a mouser's app. But for the same amount of mousing selecting the dock icon, selecting the page you want, then clicking on the icon, you could simply open up a finder window, select Applications from the sidebar, scroll down and click your app. No effort is saved with Overflow over Finder, let alone QS, PF, or DT. Why have a hotkey if you're just going to mouse over and click the icon?
I was thinking 'hey it was free and it might clean up the stuff I keep in the dock all the time' but it doesn't; running programs are still sitting in the dock so it doesn't really save you any space. If you option click the icon too many times, it starts hiding other apps. I think this is a bug. I can't see what this functionality could add.
I do like the interface, and it's neat that I can float it around the desktop so it's basically a widget with shortcuts in it. Then again, after putting it someplace nice and trying to keep it there with (what is it, control or command click?) it would close anyway, and just open up in its default position again when I re-click. I have been playing with this since we got it as loot during the missions, so it's not like I just spent 5 minutes with it and decided I don't like it. I have yet to find a real use for it, even after recreating everything in my DragThing containers so that Overflow is the exact same organization, I still don't get the feeling it's as useful. The app launches quickly, but after a few uses, it quickly gets sluggish.
Finally, I don't use Stacks, so I don't know if all of the same functionality is available with Stacks or not, but it certainly seems like Overflow only offers cosmetic differences to the 'grid' stacks.
If the developers are looking at this forum, please take this as constructive criticism; if you are still developing this app, then try DragThing. I think you'll find that's the finished product of the idea you had when creating this app.
If you missed out, send me an email. If I do get a license I'll consider gifting it if I can't find a use for it.