We use this product, and it is excellent. It is currently a collaborative team inbox with multichannel capability. Each person here who communicates with the outside world the company's behalf, can log into one place, and jointly be responsible for an incoming flow (and conversations) of email plus various social channels. (Plus website "chat", although that has some rough edges for now.) It also doesn't do a great job of handling people's individual email, and it will be nice to have individual email more fully integrated with the collaborative team in box concept.
But.
From the amount of the raise and the interview comments, it sounds like the product is headed elsewhere. Like it might loose focus on collaborative team and box features, and instead grow into (yet another) general purpose well-implemented email application, which then gets bought by one of the larger companies, then shut down, and then 10% of the features reappear a year later in the larger company's product. This would be a great outcome for the Front team, but not for Front customers.
(For those here that are questioning the price, the price isn't bad considering it typically would apply only to the smaller set of people in the company handling customer facing email, and it provides a bunch of value for that use.)