As long as they are type 1/PET, it will be fine... I'm actually going to be looking to get some of those bottles myself as soon as possible (need to locate them first)...
They should be excellent for ~3 gallon batches too...
Ya, but the extra $20 gets you a fancy better bottle sticker But ya, if your not doing small 2.5G batches I think it would be annoying to have to use two fermenters for every batch.
The water bottles, I've seen, that are ~4 gallons are not clear. Not that it really matters if they have a tint to them, since most of us know that the color in primary doesn't mean much of anything.
I'm looking to use them more for actually transporting water to where I'm brewing, right now... I'll probably be using a couple of my current carboys for this week's batch. By the next brew day, I should have either the 4 gallon bottles, or something else figured out... I'll be using my 3 and 5 gallon carboys since I'll need about 7.5 gallons for this batch...