I used 2 of the blue plastic water cooler bottles for about 6 months. One for a primary and the other a secondary. The first several batches were fine, no problems and tasted good.
I then had 2 bad batches in a row


. Both tasted like vinegar. I bought 2 glass carboys and all my beers since then have been fine.
I believe the problem was scratches in the plastic. I just couldn't get them clean without scrubbing with a carboy brush.
Now I use those plastic bottles to store used anti-freeze before recycling.