This thing is fun... for a bit
Recently, I got to ride as a passenger in a Polaris Slingshot. These things are designed to be driven like a car but feel like a motorcycle. My brother was the driver (he works for a BMW dealership) and I got his opinion as well.
The ride was pretty exciting. It definitely feels unique to say the least. You won't be able to feel like you're right there on the ground, while at the same time being protected by an outer shell.
Getting into the seat takes some getting used to, while getting out is easier thanks to a lever that the passenger/driver can pull to open the top flap above you.
Going about 50-60mph is what feels the best, as well as going over hills. You do feel like you're on a roller-coaster at that point.
Going around corners can feel frightening as a passenger because you can almost feel the right and left rear losing its center of gravity the harder you turn. As a driver, this is lessened because you are in control.
Once you hit 70mph and above, the Slingshot starts to shake uncomfortably, and you get a sense that it really wasn't designed to be used at top speeds like that.
In general, you can sense the back wheel taking the punishment normally needed for two wheels. The rear slides in a jerking manner when you turn too sharply. This adds to the excitement, but also can be worrying.
In conclusion, the Slingshot is fun to drive, and fun to ride in. But I wouldn't own one, or want to drive it every day.