This is the single best thing I have ever bought for any Harley I have ever owned.
Let me start out by saying I always thought these things looked kinda poser. BUT...I sat on a friends bike that had one and noticed that my right leg fit right up against the tank and my foot rested naturally right on the rear brake pedal. I rode it around the block and was so impressed I went to the dealer yesterday and pried $300 out of my cheap little fingers for one. There are other people making basically the same thing, but I tend to buy Harley because I know what quality level I am going to get.
Installation was quite easy, I would say a 3 on a 1-10 scale. Minimum tools needed, but of course you will need the obligatory Torx bits. Time to install was maybe 30 minutes. I already had a free flow aircleaner and run a SERT with a custom map, so I really don't know if it would need a re-tune from stock. Power seems to be a little crisper down low, but then again I run a Rinehart 2:1 for performance anyways.
As far as the rain issue goes, it comes with a rain sock, but the owner of the dealership that I go to (Paradise HD in Tigard, Or...a GREAT dealership) has the same bike with the same set-up and he said he has never had any issue in the rain and only puts the sock on when he parks it where it might get rained on.
I rode about 200 miles today on it and was amazed at how comfortable it was. No more "Harley Knee" and it was almost like I had a new rear brake. I was surprised that there was no discernable induction noise. I expected a bit of sucking sound.
Caveat- I have a Dyna with forward controls and I don't know about Softails. I had a FXST in the past and had the same problem with my right knee, so I imagine it would work just as well.