I stayed 5 days together with a friend in a double bed room in the khaosan hostel and we had a fun time there. The kitchen is well equipped and there's free internet access in the common room. The rooms and showers were clean and the staff was always helpful and friendly. They even got a TV room (not that you really need it... you're in Japan!).
It takes about 5minutes to walk to the train and subway station from the hostel and restaurants, karaoke and other shops are all near by.

Stayed at Khaosan Fukuoka for one night in June, the hostel is a little bit far from JR station on foot. Other than that i think I have no complaint about the room & facilities.

Room is small which is expected, though it's clean & comfortable. The shared shower room, toilets, common hall, kitchen & free internet were up to my expectation.

Overall, it's not bad.

My sister and I stayed here one night in a twin double. I had to stay on the top bunk and I promptly learned I hate bunk beds. Anyways, the staff here was very nice. It's kind of hidden away though, so it's a bit hard to find. There's a laundromat about a block away. The room was very sparse, but if you just need a place to stay for the night, this is a good option.

Stayed in a twin bunk bed room for one night as a stopover from Kyoto to Beppu with my fiancé. Reading the past reviews there are 2 main issues: the distance and it is fairly cheap. In fact, throughout all the accommodation booked so far for my 2 week trip this is by far the cheapest for a 2 bed room but by no means the nastiest- I have stayed in more expensive hell holes. The price is reflected in the distance from the station it is about 15-20 mins walk carrying backpacks, the last five really kill the legs. But when you get there it is clean, tidy, the staff are friendly and for a while you forget that you have to lug your gear back to the station.
We stayed on the 3rd floor twin bunk- the most compact room we stayed in so far but manageable. The toilet was near and the bathroom for each sex is located on different floors.
Noise was a real issue, could really hear passing neighbours in the corridor and conversations in the common room from our room Nobody was being loud and unruly but the noise did go down after midnight. Perhaps due to the small area, sound carries to the rooms easily.
The friendly staff did recommend for us to catch metro to the park and walk back and this was a nice stroll.
All in all, for our purpose of using this as a cheap stopover it ticked the boxes. Though I can't imagine staying here more than one night- the distance to the station/city centre would bug me. Just make sure you at least have the tasty speciality ramen of this region!