I've used it (alongside eM Client) since March this year (bought a lifetime license), and as a mail client I really like it. It's simple, fast, looks good and keeps getting updated. It's simplicity is a strength, but also a weakness depending on your needs. If all you need is a mail client it does the job, and does it very well. If you need more advanced features, or stuff such as a fully integrated calendar then you should probably look elsewhere. The same applies if you're using it with a lot of different mail accounts. It handles them well enough, but the lack of a unified inbox (for now, it is coming at some point) is somewhat annoying.