This shows you don't understand what is going on. Any person who can successfully use ADB to install an app has:
Correctly installed the USB driver for their phone
Made sure that required files and folders were extracted to the correct place.
If you do that, and have .NET4 working correctly, this program has to work. It's simply a GUI for the same ADB commands.
The hit or miss part is easily explained. Follow directions = hit. Don't follow directions = miss. Use the troubleshooting tools to submit a "bug" report, and I'll happily tell you what part isn't right. I can't do any more than that.
To the posters with Errors from ADB -- try a different apk file
OLDER_SDK -- what you're installing doesn't work with your version of Android.
DEXOPT -- you're either trying to install a system app, incorrectly signed apk, or have a corrupt apk file.
both these errors mean the SWM is working correctly, but there are issues with the apk file.