I have the HAF 932 case; had it since December 2009. Yes, it is a great case. The perforated screens in front, side, and at the bottom (for air inlet) do not serve as filters. They are screens! Little or no filtering of air is done by these screens. Serves cosmetic purposes.
There is no substitute for regular cleaning using a can of compressed air. Cleaning intervals depend on the environment the computer is located in. Three months to six months intervals would be a good start.
I already mentioned about the routing of the front panel USB 3 cable to the rear. And yes, it is done through the rubber grommets that are located at the rear for liquid cooling lines. This is how I routed the USB 2 cables for the card reader that I installed in front, and plugged them into 2 USB 2 rear ports. The motherboard USB 2 headers were all used for the front panel USB 2 ports.
My next build will also have the HAF 932 case. Very robust and plenty of room!