After a year of trolling Craigslist for a used Bobike Maxi rear child seat, I happened across a trade-in/discard on the floor of Dutch Bike Seattle at a nice price, and now we have both a Mini and a Maxi. Mamafiets here we come!
I've chosen the Globe Live Mixte for our test bike ... I wonder if it's not Dutch enough (meaning sturdy indestructible hi-ten steel) to handle 2 kids plus parent, what with its lightweight curvy aluminum frame, but oh well. So far it feels a might bit flexy, but it's a nice smooth ride. I would have used my actual Dutch bike but as it's not a step-through frame, I'd need to attain levels of yogic flexibility to get a leg over with kids on front and back.
As far as the handling goes, between the low-ish trail, centering spring, weight on the porteur rack, and a centering weight in the front seat, you'd need an advanced degree in steering geometry to understand what's going on. But so far, it seems to work.
For those in the market for kid seats, I'm a big fan of the Bobikes (not the latest Star Wars-y ones, though), although we're used to having chest buckles over here in car country. See our front child seats article for more on fitting and such. Their Dutch kid seat competitors, GMG, previously keeping alive the kind of bent-metal-tubing seats you might have ridden in "back in the day", have also come out with some great looking new Yepp front and rear seats (AKA Mini and Maxi too). All the modern Dutch trimmings are there - windscreen, "sleeping roll," and even a locking mechanism on the quick-release! Not as necessary here in the US, where folks are more likely to gawk at than rip off such setups. See them & compare with bobikes and iberts and more at Clever Cycles.
Whether you're in the market for a front or rear seat, or both, do take a look at the Dutch seats. They are decades more evolved than what you'll find in your local bike shop. They do have less "plastic bathtub" wrap-around coverage than the US rear seats you'll find, but I personally am OK with that. And for Dutch front seats, you generally need a more upright bike with some stem showing. But you need that anyway, right?
I do wonder if "Maxi" is the best branding choice for the US market (not that they currently care). Kind of like the (English) Brompton touring pannier that was recently rebranded as the "T-Bag." Perhaps the new Brompton US rep will fill them in on the multiple levels of wrong involved in that moniker. Similarly, makers of "Fanny-Packs" (which are making an inexplicable comeback with the fixerati youth) here in the US should seek branding consultation before launching in the UK. Glad I could help with all that.