Been using it as my main account for over a year, have an old gmail account which I'm giving a bit longer grace period until old clients and contacts stop emailing. Using it on iOS, it's works great but don't expect many features. Same can be said of the webapp. I use a custom domain so I'm not worried about it shutting down, I'll migrate to something else. One issue I've had is emails from new contacts sometimes showing up in junk.