Not sure where this cap is and why it would cause the winch to fail. Please enlighten me.
I'm sure it depends on what Warn (authorized) dealer you speak to. I did a lot of research and every dealer I spoke to had mostly positives things to say and none said they wouldn't recommend it. Of course keep in mind they're dealers and trying to make a buck so some may not be as honest as others but I don't believe they were all dishonest. I knew the negatives of the winches but I got a great deal on a used/demo unit so I couldn't pass it up.
I have had the HD (12,000) for a few years and love it. I plan on installing an an additional auxiliary tank but haven't gotten around to it. The compressor does everything I need it too but an additional tank wouldn't hurt. I've used the winch more often than the compressor. Never had a problem. I installed a synthetic line when I first bought the unit. For the more hard core expeditioner or off-roader, this may not be for them. It's obviously not for everyone. But, I love it.