my coworker gave me a ride in his newish Kia at lunch today, so I asked him about it. He's already had the engine replaced, and the transmission is on its way out.

It’s a Carnival for the dealer, every time they see you drive in with a new problem, which needs fixing. 

Endless moneypit, do not buy that car if you value your money.

Kia is trying everything to sell their junk. Fancy names, flashy exterior designs....but underneath all that, it's the same low grade stuff it always has been and they simply do not last.

Pass and get something more reliable if you value your money.

I would avoid all modern Hyundai group products.

I would not bother with the Kia Carnival, esp. if you plan to keep for a long time and put as much miles as possible.  Hyundai/Kia products are just not well made, esp. beyond 100,000 miles.  As for Hyundai/Kia being reliable or not, see here:

https://carkiller.com/scottykilmer/qa/hyundai-problems-master-thread-on-scottykilmer-com/#post-89418

Well the Carnival is new and it replaces the Sedona which was a pile of junk as far as I know, I would not buy any Korean car. If you rlly like it, lease it, plain and simple.