The one main issue I have with K&N's is they SHRINK to the point where they are unusable well before their million mile warranty.
They also don't cover shrinking in their warranty, so you're SOL unless you know someone at a parts store that can swap em for you.
Also, on the ebay filters... There is someone on these forums or SF that had one get SUCKED into his turbo and destroy it. No way in hell I'd ever let one touch my car...