Simplify is a browser plugin by the one-man-team Michael Leggett that cleans up the UI of Gmail.

I like it OK. I’ve tried it a few times and it tends not to stick though, probably because I have some muscle memory for some feature that’s not hidden or something and generally I’m not distracted by the default UI enough to care.
But it has lots of fans, the blog, On Simplify, gets dozens or hundreds of comments on each post. Lately, particularly on a post about finding a business model for Simplify in Choosing a business model for Simplify. Michael is going charge money for it because none of the other options feel right to him.
Monthly pricing (a few bucks) sounds good to me, especially because the pricing he puts out feels fair. I imagine it’s a decent amount of work keeping up with a third-party and making sure your vision of the UI maintains. But it’s also not, like, accounting software vital to running your business or something.
When you’re public about changing your pricing, everyone is going to have an opinion. It looks like Michael is going a good job listening. My advice? Don’t listen too hard Michael. If you try to please everyone you’ll end up pleasing nobody, especially yourself.