The best part about St George is that it is quite close to Paddington Station. Beyond that though, it doesn't have much else to offer. It's cramped, cluttered, and not particularly clean. The staff are friendly enough, but somewhat unskilled at their jobs. My room was quite small - the door hit the bed and couldn't open fully. The bathroom was a bit dodgy, and I didn't feel inclined to shower there. I don't know how the price compares, but it's probably not bad for London.
The Riverhouse Backpackers is without doubt the best hostel I've stayed at. The location is perfect - right on the river and super close to Cardiff Central Station. The hostel is clean and very comfortable. The showers are excellent, with lots of privacy. There was an amazing breakfast spread every morning. I never used the kitchen, but it looked clean, new, and well-stocked. Charlie was wonderfully friendly and helpful. I felt very at home and would stay again in a heartbeat.
K's House Tokyo Oasis is clean, cozy, and friendly. Best of all, the location in Asakusa is fantastic. The Oasis is surrounded by places to eat (there is an excellent ramen shop just outside the door) and is minutes away from the station and Kaminarimon. Unlike the other hostels we stayed at in Japan, Tokyo Oasis was not at all damp, and consequently was much more comfortable to stay in. The staff were incredibly welcoming and helpful.
If you just want somewhere to crash, K's House Kyoto is a solid place to stay, in a good location with good security. It's a large facility, so it's not especially cozy or hospitable. The corridor of the floor we were on was fairly dank, and the room itself was extremely damp. It also smelled quite badly of rot, which we speculated may have been caused by the moldering, wet tatami hanging in the alley outside our window. Not bad, but I probably wouldn't stay there again
Bonsai Guesthouse was welcoming and cozy. It is a small and quiet place to stay, a little way away from the action of Osaka, but literally just around the corner from the nearest JR station, so it's quite convenient. The staff are amazing - warm and friendly and very helpful, especially Kim-san. The Bonsai garden on the roof is beautiful, and the kitchen/lounge area is very comfortable. My only complaint would be that the rooms feel very damp, but this seems like a trend in hostels I've been to.