Are you using Marvin? I considered it but it didn’t seem to have a visible community (as proxy for life expectancy).
Things like page loads were quick enough, it was more that I was never _quite_ sure how to do things. It would be kind of close to other task management stuff I’d used, but just different enough to slow me down significantly and that initial and immediate drop in productivity made me look for other alternatives.
They do a lot of regular releases and are great about listening to users, so maybe someday I’ll go back.
But the user interface, specially on mobile, is not the nicest and fastest and they struggle to keep it user friendly due to the overwhelming set of capabilities and possible workflows. It's like the Emacs of Productivity Apps, so Cultured Code's Things or even Todoist are much much more polished and fast.
I came back to it because it's the only app that integrates well with more than two calendars, allows for timeblocking and has habit tracking.