I've had mine on for 7,000 miles or so and I've had zero troubles since I put it on. I've only traveled to a little over 5,000 above sea level from just a little bit above sea level and the bike ran great. I love hearing the roar of the engine (of course, with earplugs most of time) without the big air box.
I've had the red pre-filter on since I installed it and like another poster said, it's pretty easy to clean, oil and re-install. My only gripe is the oil I bought is super sticky and it's hard to not get it all over my hands, arms, etc. when re-installing.
I put Akros on when I put on the Rottweiler and re-mapped. The bike feels faster, stronger etc., but it was already pretty stout before, so I can only have faith that I got the extra ten or so horsepower that I read that I was supposed to get. I'm sure I didn't need the extra horsepower, but I like the changes I've made.