I just installed the Whispbars last night. Install was easy, I like that they replace one of the bolts holding the flush racks, they feel like a real solid connection (I used the foremost and aft most bolts). As to road noise I have only used them for today but so far I'm very impressed. Driving on back roads up to 40mph I had to have the radio and blower fan off to hear them. I was able to get some noise on the highway but it was also a windy morning here in MA so I'm not sure how much can be contributed to the bars.
Overall they are the quietest roof bars I have ever owned, much quieter than my old pair of square bar thule I used with a fairing and Much Much quieter than round bar Yakima without fairing (both used on different cars). I am very please with the decision to go with the S17 Whispbar, they were more expensive then some of the other options (I'm in just under $400 for the bars, kit kit and shipping), but it is my intent not to remove them and I wanted a solid connection with minimal noise.
Only other info I have right now is the center to center distance between the bars is ~33" if you use the outermost bolts.