John was a really nice host who provided us with a lot of information about Dublin and offered us help if we ever needed any.
I stayed at Johns place with both my parents, so there definitley is enough room for three people if you know each other well.
The room and bathroom both were very clean.
There are a lot of utensiles at the place though you can't really cook something except for using a microwave. It was good enough for us, because we went out everyday for lunch and dinner.
Since the room is just a single room you probably don't want to spend too much time there. But since you probably want to come here to visit Dublin you don't want to stay insight the whole day anyways. There are lots of nice pubs close by where you can try some local beer and whiskey ;)
The city centre is not really far, you can even walk there which takes a good half an hour. But I would recommend taking the bus to the city centre; there are lots of busses operating regularly which take you to the city center and the prices are ok.
We didn't have any trouble with noise during the night and slept very well.
All in all we had a really great time in Dublin and I wouldnrecommend staying at Johns place!