Installation:
I did a fairly standard system install inside the GD04 to see how things went, and to watch out for any problems. I installed a M-ATX socket 939 board with stock cooling, one 3.5" HDD, one optical drive and a Seasonic S12II power supply. Installation went without a hitch, but things are a tight squeeze, as with a lot of M-ATX cases. A modular power supply would certainly be recommended for use in this case. The layout inside is actually quite generous because the largest open space is right where the motherboard slots are. This will allow the case to easily accommodate long video cards up to 11" in length. I also noted very little clearance between the bottom of the optical drive bracket and the CPU cooler. Since most stock coolers aren't any taller than the one I used (usually a little shorter) this shouldn't be a huge issue. There will certainly be some restricted downward airflow, but the two 120mm fans are only a few inches away and will definitely make up for this. Silverstone does note the following on their website about this:
"When optical drive is used, the GD04 has 70mm height limitation for CPU cooler. If no optical drive is installed, the height limit for CPU cooler increases to 120mm"

(I left the optical drive out in this picture so you can see how the cooler comes right up to the base of it)

Testing:
Since I have already commented on the high build quality and attention to detail this case has, I will look mostly at the included cooling system as my source of testing.

The GD04 focuses on positive pressure cooling, that is, it pulls in more air that it outputs. This is done by the two 120mm fans on the one side sucking in all the air, and the single fan on the other side (as well as the grills on the case) are taking care of exhausting the air. There are many debates as to whether positive pressure cooling is better than negative pressure cooling, but the one thing that is for sure is that it helps keep down the amount of dust in your system by "blowing" it out. Keep in mind you need to keep those fan filters clean or your airflow will really suffer and could lead to overheating issues if left too long.

Overall cooling noise levels were quite impressive for the number of fans in this case. All three 120mm fans run at 1200RPM and have rated noise levels of around 20dBA. The frequency of the fans is a very pleasing one, I had the case sitting only 1 meter away from me on my desk and it did not get annoying at all during testing.