Mercures are usually pretty nice hotels, but this one is a bit below their usual standards. That said, it is a very good value and the location is smack dab in the CBD.
I stayed 2 nights in a standard room. It was small but looked like it had been recently renovated. The TV was the old style and had limited channels. You pay for WiFi. On the plus, the bathroom was very clean.
I could hear noise in the hallways, but I'm a heavy sleeper so it didn't bother me too much. If you're a light sleeper it might be a problem.
If you're looking for something a bit nicer, the sister hotel Swanston Grand Mercure is just around the corner.