I am actually using several UI modules to help speed up my game development. If you think about elements like options, in-game currency store, level select, etc. the fact is that users don’t really care how most of these look as long as they work as intended and expected, so having created an overlay IAP store that I can move between projects has greatly sped up my team’s development speed. Same with options since no one has to spend more time than absolutely necessary with something that users don’t care for.
But, regarding whether I’m interested in additional UI or widget frameworks, the answer is yes, if they serve a function that I need and haven’t already addressed. The more universal or broad the plugin, the less likely I am to need it, whereas the more specific and niche it is, the more likely I’d use a plugin for it.
While I don’t mind closed code, I think twice before implementing such plugins in my projects because if something breaks or if the plugin becomes unavailable, then my projects will stall or require code rewrite.
That being said, I am also planning on releasing a free simple “window UI” plugin next week to Corona Marketplace, and I’ll also provide the code for the plugin on my company’s site (and my personal GitHub) once I finish the company site’s redesign. I have also thought about providing other UI modules that I use as plugins, but they would require more work (perhaps too much) to turn into plugin form. Some such UI modules are the aforementioned IAP store, endless level select scroll setup, etc.