I just put about 1000 miles on the new 19" front and 17" rear and I have to say that KTM made a HUGE mistake by not making this the stock wheel size on the bike. I think they should offer the 21" and 18" wheels on the S as an offroad biased bike but on the street that size isn't as good as it could be.
I think the 17/19 combo is so much better since it puts a quicker steering and wider front tire on the pavement. The bike turns in quicker, transitions much faster and easier and feels more planted. There are also many more tires available for this size and it takes about an inch off the seat height.
I'll keep the set of wheels that Woody made for me that are beefed up in the 18/21 sizes for when I plan on doing some serious off roading but if I'm going to do any long trips I think the smaller wheels are much better suited. I'm thinking of putting a set of TKC 80's on the new rims and doing the 1-State Dual Sport coming up in May just to see what they're like off road but I did a few gravel roads on them and it wasn't bad. I'm running Avon Distanza's right now so that's a more street oriented tread but it wasn't bad.
I think the improvement of handling on pavement (where 80% of these bikes will spend 80% of their time) is more than worth the small trade in off road ability. If this bike had been tested with these wheels against a GS, Multistrada, Buell or V-Strom it wouldn't even be close. This is the perfect middle ground between motard 17's and the full offroad wheelsets and it makes the bike a real pleasure on the pavement.
I spent a lot of time on small twisty back roads with these wheels and I can't think of any full size bike that I've enjoyed flogging as much. It's a complete transformation.
Clipper - you'll have to try it to believe it.