wmbattery is the only end user GUI app I have ever written for linux. It's the only program that I forked from someone else's existing program (if you don't count debhelper). And it's the only program I've done that was partly designed in Microsoft Paintbrush in Windows 3.1.
A lot more people have ended up using it than I ever expected, and the coolness factor of seeing it on someone's desktop makes me understand why end user graphical programs are so appealing to a lot of programmers.
I think it succeeded because it worked well, was intuitive to understand, looked pretty neat, and was influenced by the underappreciated "calm computing" movement.
It's lived for a suprisingly long time, for a graphics program that was after all designed to be used with just one or two specific window managers. I still have it running on my ion desktop, where its mataphore is completly out of place. But it's sunk into the background for me, and I suspect for other users, and it's not worth giving it up for something that's a better fit with the rest of the desktop.
Oh, MS Paintbrush story is that I was home for Christmas, the computer at home was running Windows and I ended up forcing my sister Anna to help me do the graphics for wmbattery a pixel at a time in Paintbrush.
Thanks for your wmbattery. I use it with ctwm on gentoo and centos for years. It really is the only acpi standalone x11 app out there. Good that you have it in git now. -Peter