I just started readingthis thread but will comment here on the basic question. I don't use bladders. I do carry nalgene bottles (NB) daily...I use them at work, running around town, in the field, etc. I also use the insulated covers made by OR (can get them at REI). The covers are a bit steep, but I have 4 that have been in heavy rotation for about 15+ years. And while some may find them not worth it, fully iced and loaded, you can get cold drink for HOURS...in fact I've tested them in hot cars in the summer and after 7 hours over 120 degrees, still had cool drink. Is that necessary? No...but little comforts can mean a lot.
In my emergency kits, I've added the Space Saver Cup (Campmor). They fit in the bottle jackets with the bottle.
Now, why NBs???
I figure the best tools are those you WILL use and have nearby. I am always with a NB so they are a given. I find them convenient and tough. I find them easy to CLEAN...something I find important. The wide-mouth access means I can use them for more than just water. In BOBs, they can also house "likes" such as instant mixes, purification pills, plastic tubing, etc. BTW, they also provide a waterproof place for stuff that needs to stay dry. With a couple of bottles I can purify one and drink another. I can settle out solids in one as well. Flooded areas suck for getting water.
All this said, bladders fold up well and can carry quite a lot.
But to me they're more difficult to handle and clean. Impossible? clearly not...just more hassle. I am considering a few as backups, but unless SHTF, I can't see ever using them. I've got a good number of NBs. <img src="/images/graemlins/grin.gif" alt="" /> <img src="/images/graemlins/grin.gif" alt="" /> <img src="/images/graemlins/grin.gif" alt="" />
Oh...and I don't work for Nalgene!
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...got YAK???