This is a front-mounted child seat. There is a clamp which goes around the stem (or the steerer tube if it's a threadless headset) and the seat locks onto it. Your child ends up behind the handlebars.
Ours was bought second-hand; supposedly it's about 5 years old. No dramas there; it's been looked after, but for all I know there have been changes and/or improvements since (current models have a "+" in the name. I have no clue whether ours is a "+" or not).
It works pretty well. There's more room for my knees that with the WeeRide that we've also tried. I still have to pedal in a slightly (more) wierd way than usual, but nothing too terrible. We use it on our Yuba Mundo, so (1) it's about the least twitchy bike I've ever ridden and therefore doesn't mind 8-10 kg perched over the front wheel and (2) there's plenty of weight (ie the other two kids) in the back to balance things. I wouldn't try it on a race bike, mind you, but I expect that something with fairly relaxed steering would be fine.
Assembly is pretty easy - clamp the bracket onto your stem and away we go. Supposedly it works the same if you have an Aheadset system with 25mm of spacers. It worked fine on a 1/1/8" quill stem, FWIW. There's some other attachment device that has to do with mountain bikes, so it should work with most sane bikes. My smokin' hot installation tip: a tap spanner (I think that's the term - a long tubular socket) helps no end: the bolt sticks out too far for a regular socket spanner and there's not enough room to turn an open-ended spanner very far.
Once the bracket's on, it's about a 5 second job to take the seat on and off. You pull out a split pin and slide it off. Putting it on again is just about as easy.
The back doesn't stick up far enough to get in the way of a helmet, which is a good thing, what with helmets being The Law here in .au. Our little one (ca 9 months old) falls asleep on it, helmet and all, which is a ringing endorsement of its comfiness. It'd be good if she had something to rest her head on. I gather there's an accessory for that which is on the wish list.
Getting on and off is a bit of an experience. There's not quite enough room between saddle and BoBike, so I need to be able to touch the ground while seated. I also have to lift my leg over the top-tube; trying to swing it over bars or back wheel isn't going to work. Fitting three kids on a bit is pretty easy, but it's not quite trivial.