I have them in my 07 WRX right now. They've been installed for about the past 10,000 miles and I haven't experienced any negative issues with them, besides dealing with the fact that they're so expensive. I didn't measure my hp, torque, or gas mileage before or after installing them, so I can't honestly say whether or not they improved any of that like the advertisements claim they do. It would really help me to see before and after data of them installed on another WRX to help me justify spending that much. I'm not so sure I'd get them again simply because of the high cost.
My overall impression: they're ok