I actually stayed on two different occasions in this hotel like 3 weeknights. The hotel has been recently redone and it's in pretty good shape. Good wifi, really helpful and friendly staff that even remembered I had stayed there. The only not so good thing is that the A/C is not very strong and the room never got colder than 25C so I did have to close the window curtain at times to get the room cooler. I got a corner room both times with a big window.
Some reviews talk about the area being the red-light district and even locals told me the neighborhood had prostitution. The hotel is just in the edge of the neighborhood, I saw NOTHING bad, there are restaurants that are always full and even many late night restaurants around the hotel. One block away you are like in a big avenue with the parks of the National Stadium. I think it was really a really good location.
Other locals I talked to said that the Hotel 81 brand was seen like as a motel but at least this location of Hotel 81 was just like a normal hotel, I saw families and everything was just normal and ok.
Some other reviews complain about the bathroom not have a shower door / curtain... well, that's South East Asia :) I just didn't open the shower all the way to not get the floor too wet but it wasn't an issue, I would just put the floor towel after the shower on the floor and that worked.
After two stays there, I would stay again. Overall excellent price/value ratio, specially for Singapore.