I'll definitely check them out. Picking a new email provider is really hard, reliability is key. And to me gmail used to represent the ultimate reliability, but no more.
On the other hand, they're a lot more transparent than Google, their special sauce does not include their infrastructure, most of which is open source or they've open sourced, and no doubt due to their singular focus and relatively smaller size you can get contact real people rather easily, sign up for updates on their software and infrastructure, etc. Google is so big that, as you've discovered, they don't have to care.