Room treatment is VERY important. I had to become an expert in acoustics when I was trying to get a square room to work. I ended up using a diagonal set up in the end, but in the mean time my obsession caused me to read books, articles, etc.
I'm glad because I know feel like I can tweak a room by ear and know exactly where to place everything. An untreated room with some bad dimensions can take a solid set up and make it almost un-listenable. Room acoustics are THAT important.