I'm a recent convert and can't come up with anything negative so far other than "Why did I wait so long?".
I've been following the darkside threads closely for three years now trying to make my decision to go for it. I've read every single thing written on the topic here on this site. I've weighed both sides and eventually took up the dark cause arguing for it before I had even tried it just based on video, debates and reviews.
The only negative reviews were not even reviews, they were blatant outright attacks and propaganda lies posted by guys with phobias and biases based on B.S.. The comment that raised the most eyebrows was that hard cornering rides on the sidewall and could lead to premature tire failure. As a newbie to the car tire, I pressed the bike hard to verify if this had any merit whatsoever. I put more wear on my floorboards in the last weeks than I had done over the life of the bike (and I had to replace the feelers once when I had pegs). Now that I've just about reached the point of replacing the feelers on the boards with the new ones left on the pegs (in a box), I've concluded that there is no possible way to corner hard enough to touch the sidewall on a properly inflated car tire. No Way, No How ... can't be done. If you can scuff a sidewall, you don't have enough air in the tire anyway. And you didn't scuff the sidewall ... it folded up on you.
I noticed right away that the bike had a slight tendency to want to stay upright when compared to the bike tire. That feeling lasted about three days, then I never noticed it again. If you've ever slowly ridden over a curb or pothole at an angle with the fat 240 Metzler, you've noticed the tendency of the tire to tip the bike due to it's width. A car tire makes that a little worse, just a little. I've backed out of the driveway over the curb and got uneasy from it trying to tip. I'm used to it now and am always ready for the leverage the wide tire exerts tying to tip the bike. Since I know it's coming, I'm prepared and expect it. That is the only bad thing I can say about it, and the Metz did it too.
The ride is softer, the cornering is steadier, wet traction is better and the tread depth is awesome. You can put a 15,000+ mile tire on the bike for $140 and be used to it's quirks in a week ... just try it out. If you don't like it, go back. But if you give it a chance, you won't go back ... not on this bike.