Well, just installed and I rather like it. Sleek design. Simple interface. RSS is a good addition. Sadly, though, no auto-feed discovery like many RSS clients do nowadays.

At first glance looks more appealing than Thunderbird. Certainly so in configuration, which is simpler and more intuitive. Thunderbird's single SMTP pane for all accounts annoys me each time I see it.

Lacking vertical positioning for the "List and Message below" layout. But I guess it's just a bug.

They launched it very timely, when the cloud is no more to be trusted. Behold! The return of the desktop app! :)