I rode the River Journey twice. Yes, I'd like it to have been a bit longer, but I think the larger deficiency is the "what the heck is going on" element. It could be fixed by on board audio, by signs in the queue, by a welcome message from the Navi delivered via screens in line, or even by an informational pamphlet from the PCI. As is, there's really no possible way to figure it out even if you try, until you ride the thing. And even then, it's not quite clear. The lack of story didn't bug me, but the lack of context did. The "Field Guide" provided a bit, but I'd have liked more.
That being said, I enjoyed it, and I think it's exactly the type of ride DAK needs -- friendly to all ages, no scare or thrill, interesting things to see, and indoors.