I found a bug that users should be aware of. Because this is a critical bug that can delete your settings, and because AppBolish does a HORRIBLE job of uninstalling, I will only give 1/2 star. And IMO the $40 price is at least double what it should be IF it worked correctly, which it doesn't.
BEWARE: I tried AppBolish because it says it can find leftovers from uninstalled apps. It found 43 plist files, one savedstate folder and one folder in Application Support.
Almost ALL of the preference files it thought were leftovers actually belong to installed apps! In fact one of the apps I just installed a few hours ago and ran once to test. Good thing I didn't just allow AppBolish to clean everything indiscriminately!
Then I tested the uninstaller by dragging several apps into it and also into AppDelete. I found the uninstaller does a VERY POOR job. For the first app, AppBolish found 3 files, AppDelete found 7.
Then I dragged App Store into both apps. AppBolish found 6 files, AppDelete found 12 (five at root level in /private/var/). I don't want all that junk left behind when I uninstall!
Then I dragged a simple app in (only the app and its pref file). AppBolish only found the app, AppDelete found both files.
Then I dragged Cocktail into both, AppBolish found 4 files, AppDelete found 6.
As you can see, AppBolish missed files in every instance.
AppBolish also does not show file paths, so it's very difficult to go check or remove them on your own.
One of the plist files that this app creates is named com.kallaxa.AppBoish.plist. Evidently the dev. decided to spell their own app's name wrong so it won't conflict with the other file it creates, named com.kallaxa.AppBolish.plist. They should have given it a unique name and spelled it right.