I ran one on the old girl for 80,000 miles, they clog up faster then an oem but a wash and a fresh spray of K&N oil and they are good as new, garuanteed to fit or they will give you a new one. I broke one and they sent me another one free of charge - I trust the K&N from personal experience, they require maintence but then again so does the OEM or rather replacement or blowing it out.
@duchgixxer - step one is not required if you undo the snap in as shown. Of course if your changing the oil then by all means go for it, add 5 minutes
My buddy said that K & N is okay in a "passive system," (like my FZ's where the filter is behind the motor), but he didn't like them in ram-air applications or on cruisers where the air-filter is fed by a big scoop. He says they flow more air because their gauze-like media has bigger "holes." This lets more dirt into the motor... Not the most technical explanation, for sure--but that's perfect for me, (-I can barely change my bike's oil!!).
I change the K & N on my FZ at the beginning of every season...I've never washed it.