The design isn't the most optimal for air flow but it really isn't that bad. The filters are part of the assembly that attaches the fans to the chassis. So the filters sit flush with the fan. There's a decent amount of space in front of the fan/filter to draw air from the side vents on the bezel. So the side vents on the right and left of the bezel are the air intakes for the front fans. The fan doors are pretty much there so you can easily get access to the fan/filter for cleaning or removing/installing.
Unlike the Antec Performance One cases, the side vents on the Fractals are located behind the fan doors but in front of the fan/filter. While on the Antecs the side vents sit in front of the fan doors. Basically on the Fractals the fan can pull air directly through the side vents. While on the Antecs the air is pulled from the side vents through the grill on the fan doors.
I'm a big fan of the Antec Performance One cases. I was planning on getting a P183 before I got my R3. Antec really needs to update the Perfomance One cases. It really sucked paying for the shipping to get it to the States from Canada.
Fractal: Fan--->Filter--->Side Vent--->Fan Door--->Bezel Door
Antec: Fan--->Filter--->Fan Door--->Side Vent--->Bezel Door (BANDIT_COROLLA's picture from the "Official" Antec Performance One Owners Thread
The fan snaps in to the assembly and you have the option of using 2 fans screws.
The fan actually sits flush with the filter.
Here's a pic with the front bezel detached from the chassis.
There's actually a good amount of room for the fans to draw air from the side vents.
The stock fans that come with the R3 are only 1300rpm. If you want more air flow you could always get better fans. I currently have the 2 stock fans in the front. I also have 2 Scythe S-Flex Gs on the top and 1 in the rear as exhausts. I got some Zalman ZM-F3s in my closest but I haven't bought a 3 pin power cable splitter to use them with my Lamptron fan controller. They would definitely pull more air in than the stock fans.Edited by stimr2 - 12/9/10 at 8:45pm