I've got a big head (62cm hat size) and even with the straps un-velcroed and the ends just sticking out sideways, there's more pressure than I'd like on my face. Experimenting with the facial interface on and off, I've also noticed it seems like the image warping that is done to correct for the lens distortion isn't correct for how far away the Rift sits from my eyes. With the facial interface in, if I turn my head side to side in Oculus home while being aware of (but not really focusing on) the vertical lines of the game icons and trees in background, it seems like the top corners warp inwards as they get close to the screen edge. But with the facial interface removed and my eyes a bit closer to the lenses this doesn't occur. It also feels like my FOV is less limited with the interface removed, I can see the side edges of the screens if I look straight forward, but with the interface in place my FOV is limited by the round curve of the lenses. My ipd is 65mm btw.
My plan is to try to get a more suitable facial interface 3D printed, so I'm experimenting with creating/scanning a 3D model of the original (and of my head) and modifying the interface to suit me better. So far I'm at the scanning stage. David Laserscanner wasn't working for me, 123D Catch looks like it generated more usable results, I'm waiting for ReMake to finish processing the same images to see if that does it better and I also have a xbone kinect sensor coming that I'll play with and see if that works...
I've seen other people mention getting better FOV by removing or reducing the thickness of the facial interface, but I haven't seen anyone mention incorrect screen warping before.