Yes, I bought one last week. Used it once for about an hour so far, so can only really offer first impressions.
Pros: Son (2) is quite happy and comfortable it it, and he's a picky little B and will let us know if the slightest detail is not up to scratch. The bike is reasonably easy to control with it attached (although I have no experience of other types of seats so take that as you will). Very good for enabling on-bike child/parent chatting, which is why I went for it in the first place. Very easy to get on and off the bike, five minutes with an allen key, tops.
Cons: it's big, this can make getting on the bike a bit difficult because the space between saddle and seat is a bit restricted; I'm 5'10", if you're much under that you may find it a problem. It appears to have interfered with the headset, which required tightening up on a normal ride after I'd taken it off – not a big deal but definitely something to keep an eye on.
Overall I'm pleased with it: it's not perfect, but it does the job well enough and allows me to chat to my boy whilst we're riding along without taking my eyes off the trail.