I own an HAF-X since a year or so and I am loving it. Great airflow, lots of space. The only case I would see better from CM is the monstrous Cosmos 2 but it come with a price too. I don't know much about other company's cases but I love mine. I recently moved the side fan to the top and bought another Megaflow for the side. Although I can't seem to see any temperature drop, it does help provide fresher air. I had some problems closing the top part because USB cables were hitting the fan but once forced-in, everything is running cool and quiet.
COSMOS II - Cooler Master - Leading Provider of Computer Case | Cooler | Power Supply Gaming PC - Need your opinion (My rig when I got it last year)