All services-based businesses have variability. A good review of any service includes experiencing them more than once to even that out. Good restaurant reviewers do that (and why you have to sift through the junk that is Yelp to get the real picture).

That being said, I've had good and not-so-good experiences with United. And good and bad experiences with DL, AA, BR, etc.

I think the reaction that FlyerJT is getting is "United may be a crappy airline, but it's *our* crappy airline."