I've done a bit of research on this, as I've considered doing it. I did it on my Honda for a bit. I know there are a few guys 'round these parts riding dark side, and more on raiders. My problem is, since its a new bike there's not really a lot of experience to pull from when chosing a tire, and picking a bad fit bit me when I was going darkside on my Shadow.
The pros: It works well. In most "cruising" situations, a car tire will usually perform better than a motorcycle tire. More traction in the rain. They last more than twice as long. They're cheaper. For me, burning through two or three back tires a year on just the Stryker, not including my other two bikes, it seems like a no brainer.
It's hard to get a bead on the real cons, since most of the downsides I see are from people just shooting from the hip because they don't like the idea.
BTW, from what I've read people usually run a little bit higher pressure in CTs. Like 38-42psi. But it depends on the tire.
And, WLFPAK, motorcycle tires on cars are actually pretty popular in some circles 8)