You can't ask for a better location; you're in the heart of Boston, and the amenities the city offers are but a short walk away. The room itself is as advertised—it has just enough, and having towels was immensely helpful (the small Christmas tree, albeit a fake one, was a thoughtful gesture too).
Checking in and out requires a key cafe, indeed. This wasn't a problem for me, as I didn't have much luggage; but for those that do: include visits to this key cafe in your plans (it's probably a short walk away). It was my first time using one, but there were pretty straightforward instructions sent to me by email. Moreover, the staff would reply quickly, even though it was around Christmas.
The only real issue I had was cleanliness. The bathroom towels had strands of hair, which I found on the bathroom walls too. The floor also felt a bit dusty, while the heater/cooler unit frequently spat out debris that would land on the floor. There's a vacuum, but it was an unpleasant situation.