I'm also a big fan of the polymer Better Bottles, which weigh less and are more forgiving than their 3, 5, and 6 gallon glass carboy counterparts.
Those 6gal glass bottles are freaking heavy when full!
A 'problem' I found with my 1 glass jug is that it holds about ~1L more than the Better bottles of the same size.
I'm always eyeballing the racks of 5gal water cooler jugs at Home depot- I've never heard of a definitive reason why these would be bad for fermentation/aging, but have heard a lot of speculation about permeability or other voodoo reasons not to use them.
Anyone have any hard evidence for or against these?