>"Just curious, if you don't use the Hoser (hydration bladder), and just a Platy bottle, do you just store the bottle in the pack? A 2L bottle seems like it'd take up a lot of room."
When I had to carry extra water recently (Hells Canyon, tough routefinding, some dry stretches) I had a biggish pack and volume wasn't an issue. Filled the platy, put it in the main pack bag. Not to be flip, but a full 2 liter platy takes up about 2 liters of pack volume, not that big a deal in a 58 liter pack (and it's a soft 2 liters as well, so conforms to space better than a hard bottle). On that trip, I carried two 2 liter platys, as they were intended to be used for a PFD to raft across the Snake River. Never had water in more than one. I'm sure 3 liters of capacity is overkill most places I hike, but at 1.3 oz for 2 liters capacity, and virtually no volume when empty, it's a hard habit to break. And they make a nice cushy pillow.
I carry my 1 liter poweraid/gatoraid bottle in a side pocket, which is easier access as well (maybe take a drink every hour, if it's not hot. Hydrate well in morning and evening and at water sources). With a 25 liter pack (which I can use for 3-4 nights now) the platy would prob. take up too much volume. I could go with a 1 liter platy "soft-bottle", and save a few tenths of an ounce over the poweraid bottle. But as I say, the hard bottle is easier to fill, basically free, and has a certain reverse snob appeal.