Yes I downloaded it onto my 1520. It has been a continuous rat's nest of trouble and problems (live tile not working, "unknown error occurred" messages when trying to set up basic settings, etc.). I've written to the developer with details and am waiting for his response/advice. I read some other comments in which developer was saying it's a Windows 8.1 OS problem. For now, I would recommend you stay with the default email client until MetroMail is properly fixed, updated and maintained!!
MetroMail is dead. The developer promised some translation a few month ago. And everybody how would help should get metromail for free. But there is no location update until now. He didnt responsed in the thread for the translation and he didnt give away the promised free metromail to the helpers. Here you can take a look at this thread:
You should better support Maestro, it just a preview until now, but the developers are pushing out updates very often and are going to add more and more e-mail provider and so on.
Here you can find some infos about Maestro and a link:
Am new to WP, about 1mth now.
Metromail free works fine, and has a much stronger use of Labels than native mail app. Also easier to star and archive mails.
Tried both for a week, and stayed with metromail.
Will be interested to see pros n cons of using native mail app too.