Not something you'ld want to put on if your one of those guys that comes out of your favorite watering hole, fires her up and hits the trail immediately.
Installed, adjusted and used properly they work very well. Installed or adjusted wrong or used improperly they can contribute to engine failure. The key is to take it very easy for the first minute or so after setting with a warm engine. The reason is that the Tempaflow materials have expanded due to the engine warmth and need to be given time to adjust to the real intake air temp.
The benefit is that it allows you to jet for very cold temps and still be good for warmer temps.
Put 1 on my 02 at 3,000 miles. 10,000 miles later, it's still there LOL! As Ding posted, proper install and allow a minute or so after stopping to let it readjust and you'll be fine. I ran it in Manitoba at -30f and around home in the 40's. Ran the same every time.