This place is excellent, once you find it. My taxi driver had a tough time locating it--it's on Rama IV across the street from the university, past Lumphini Park. If you're coming from the airport, you'll turn left into an underground hangar/drop-off area that I suspect is pretty easy to miss if you're not looking for it. We did a few laps of the block looking for it my first night in Bangkok.
Like all of Thailand, there are scams afoot here--I showed up the first night having botched my reservation and couldn't afford the regular rate, so they had the bellboy recommend me a different hotel. He took me outside to a dude by an unmetered cab, and that guy drove me down the street and around a corner to something more like a brothel--then tried to get me to stay there for basically the same price as the standard Mandarin rate.
But, if you simply reserve and check in, you won't run into that. This place is well-equipped, clean, responsive and pretty luxurious for the ~$45 price point I kept finding it at. It feels new, and I suspect these deep deals are in place to get people in the door during its opening year. If you're looking for a four-star stay for a guesthouse price, this is what you want.