It's a very good idea.
Some people will tell you hub gears are "heavy". They forget how heavy a derailleur mech and a rear block are.
Some people will refer to the friction losses in the planetary gears, forgetting that a derailleur chain is seldom running straight from chainring to sprocket.
A hub gear is simple, clean and low maintenance.
I don't specifically know about the 2 speed version. I do know that the usual 3 speed has direct drive for the middle gear. Top gear is direct drive plus 33% and bottom gear is direct drive less 25%.
The point is that one ratio is direct drive with no friction losses in the gears, and one goes through the gear train with a small amount of friction loss.
A keen cyclist with a 3 speed sets up the middle gear at their preferred "single speed ratio" and saves the high gear for downhill or downwind, and the low gear for up hill and up wind. It's like 3 single speeds in one.
With this principle in mind, you can set up your 2 speed so that you have "normal ratio" plus a low gear, or "normal ratio" plus a high gear. Whether you prefer to have that extra option on the ups or on the down is up to you.
As for the coaster brake, aided and abetted by a conventional front brake, you will have a very relaxing and enjoyable ride.
A small part of me is jealous. I cannot afford another bike (2 bikes, 4 unicycles, 1 ultimate wheel, 1 motorbike, 2 boats, 2 kayaks in the garage already) but I'd like another hub geared bike.
Enjoy, and ignore the critics — most of whom have never ridden one.