They are super expensive. I researched them like crazy before my baby was born. I got a babyjogger performance with 20" wheels and it was wonderful! I was really worried about him bouncing around too much. Having not used a stroller in years prior to using it, I didn't realize until many months after I had it that it was really a good stroller (I tried one of my friend's). You barely had to use any of your own effort to push it.
Unfortunately, because it was so wonderful, it was also VERY large. It wouldn't fit in my car--I have a Jetta. (it did fit in a friend's jeep liberty)
I ended up exchanging it after about 8 months for a Bob. I enjoy it a lot. It's not quite as light, nor is it terribly small, but it does fit in a sedan, and I can use it on rugged trails.
I hope this helps!