With the side panels removed, you can see the internals are VERY sparse. The wire harnesses for the four USB ports, Audio IO and Power switch and LEDs are visible, as is the Molex 4-pin connector for the 120mm fan in top.
Along the rear of the image you can see the lower of the two braces that have the nuts that the motherboard screws to.
With a simple setup of MATX motherboard and 3.5 inch drive, this image illustrates that you will be needing to plan out your wire routing a bit, but not TOO deeply to ensure proper air movement.
With a decent low clearance CPU block, there should be plenty of airflow through the case as well as the typical heat sink effect you get from having an aluminum case to provide adequate cooling for all but the highest horsepower systems.
With a spare 7 inch long PSU installed, the space looks MUCH more cramped than it did previously. If you have are looking to get this case, aim for the 7 inch length PSU, and go MODULAR. The less wiring you have to run in this little box, the better.