I installed them on my last Ultra. They are better than no vents... but are NOT like having the lowers off. And they only work when the bikes movin'. Sitting at a light, etc. is just as bad as before.
The work involved in installing, isn't worth it to me to do a second time (although if you find the vendor at a rally they'll install for free). I've built engines, bikes, etc. And cutting the holes in the lowers was the most stressfull thing I've done! Don't know why, maybe it's just me!
Living in Chicago, we get everything from 35 below to 105 degrees! I'd rather just not have them on. So as soon as I brought my new bike home I took the lowers off and accepted the fact that they will be collecting dust forever. The lowers ARE convenient but not worth dealing with in the heat. I've considered getting another set of vents... but they just don't do that much unless you're on the highway.