The worst flight attendants I've ever had on CO were EWR-based. That's not to say they're all that way; it's just happened more times than not.

I generally have had great experience with IAH-based international crews, with one exception. There was an IAH international crew working SFO-IAH on the 762 about two years ago that was downright awful. During boarding, I walked by the flight attendant in the door who was directing passengers and headed for my seat. I didn't show her my boarding pass for her to tell me which aisle to go down, and she came running down the aisle after me and asked me for my boarding pass. I had already put it in my bag, and at this point was standing next to my assigned seat. I told her I was at my seat and she said "show me your boarding pass!" I dug it out, and she snatched it out of my hand, and then said "ok - but when we ask you for it when you get on the plane you must show it!" That was just the start. During the flight they did one drink service during the entire flight (normally it's two; I've even seen a crew do three services on this flight), and refused to give passengers full cans of soda even when asked. This was back in the day when the full can was standard, before they downsized to just a cup unless you asked for the can. The meals had barely been warmed up, so the hot sandwich that day was almost ice cold. They also didn't start the entertainment system until we were an hour out of SFO, and then shut it down completely about 50 minutes out of IAH. As a result, none of the movies had finished playing. A lot of passengers who knew that the practice is to start the system shortly after takeoff and turn it off after the descent has started complained, but to not avail. By the time we were 40 minutes from landing, the FAs had completely readied the cabin for landing and were back in their seats, where they had been most of the flight. It was one of the few times when I complained to CO.