Not sure if anyone on here with an '08+ WRX has done the seat mod. I did it on my '10 and now my '11 and it makes a world of difference. With this mod, the seats will actually hug you more and it just feels so much more stable and comfortable. It's pretty simple, but here's what to do:
1) Unzip back of seat
2) Locate the metal rods (3) hooked on each side, which you may need to create a small opening in plastic to access
3) With pliers, unhook the metal rods from the plastic pieces. I did both sides, but should work with just unhooking one side
4) Zip the seat back up
5) Sit in seat and feel how much better it is.
Obviously this can be done for the passenger seat as well.