For your normal, run of the mill, weekend races you will be fine to use wheels without the stickers on them. If you are doing any nationally ranked races (NRC races, NCC crits, Elite or master's national championships, or any UCI sanctioned races) then your wheels will have to comply and the sticker will be needed on the wheels.
My biggest gripe is the UCI tests the the exact same tests we already do for EN standards, we just get the "privilege" of sending the UCI a big check and a lot of wheels for them to destroy for the "honor" of being UCI certified.
So for our wheels next year, we are probably going to add another small sticker next to the one the UCI will require.
