It reminds me of Microsoft's Outlook, which has only one big advantage, compared to other mail services – it doesn't require a browser. This feature might make me try it.
As I came across this program I thought that it might be useful to have access to all e-mails without having trouble with switching to different tabs. The main advantage of this application, to my mind, is that the browser you use is not slowed down because of the multiple tabs. On the other hand, this might be a problem if you have more than two mails on different e-mail hosting websites.