I love Nalgenes and I love this bottle, both for different reasons, but this is just such a unique container that there's more to say about it:
well, first off, it's cool. How often do you see people walking around with a squishy pouch of liquid held to their lips? Yea.
I first caught sight of one at a camp I went to, where a counselor was just loving the cool misty flow of dihydrogen monoxide down his throat, and I was loving it too...the thought of having my own! Oddly enough, water seems to be colder in one of these than in a Nalge. Probably due to science.
One very self-evident feature that I cannot leave out of this rant is how it folds up...! it's awesome. Say you're going on a hiking trip where water sources are limited at the start and you hope to resupply at streams as you go. Well, folks, pack down one of these Platypi somewhere in the depths of your pack and it takes up as much room as a nalgene would if it were crushed plastic without dead space. Essentially, it's an extra liter of water you know you can drink without taking up an extra liter of space in your pack. YA platypus, I love you