The self check-in was described in detail and worked well! We didn't meet our hosts in person, but they were always helpful and replied quickly :)
The apartment is located in the same building as a very good bar/restaurant which we highly recommend for its good food and drink selection. This, however, means that you'll also hear some music and noise coming from the bar until they close (which was before midnight during our stay). It didn't bother us much, but the walls are quite thin in general and we were woken up several times by people walking and talking loudly in the stairway. This is not the hosts' fault, of course, just something to consider if you're looking for a particularly quiet place.
The apartment itself is well-equipped, very clean, and in walking distance to the historic center of Riga, with plenty of cafés and eateries right next to the building. All in all we enjoyed our stay!