I've been travelling around the world on a motorcycle and have stayed many hostels during my trip, and Grammy Hostel is one of the best I stayed. It's clean, cozy, fun to stay (almost every 2nd day has a party at the common area!), and it has super helpful staffs!
I planned to stay for a few days only but I ended up to stay for more than a week! I loved to stay there.
I could park my motorcycle securely at the hospital behind the hostel.
I do recommend everyone going to Yerevan to stay at Grammy Hostel.