By "PET" I don't mean "meow meow," but rather the Better Bottle, plastic
carboys that have been brought up before. I bought one a few months ago
and found it much more manageable than a glass carboy. I haven't
noticed any problems in using plastic, other than it being slightly
fussy to clean dried crud from the very top of it--soaking it
upside-down tends to loosen things up. The only problem has been heat.

I was following one of Jack Keller's recipes for making cranberry wine,
which required introducing hot water into the container. The water was
to be poured over the fruit and sugar. Unfortunately, this heat caused
the carboy to implode a little bit. It was like microwaving cheap
tupperware with the lid sealed. The container isn't what I'd consider
damaged, but I wouldn't be doing that again with the container either.

This wasn't mentioned last time these carboys were brought up, so I
thought I'd contribute it as the only downside I see in using them over
glass carboys.