My rig is much better now but I always feel something. Maybe I'm more sensitive. My wife says that she doesn't feel anything anymore (no jokes please) and that I will never be able to tow a trailer without feeling like the trailer is not behind us (I know, contradictory statements).
Anyway, this weekend I saw a pickup truck pulling a trailer the same size as mine swaying like crazy. He was at around 65 mph. Every truck or TT rig that passed him on the left would push him to the shoulder.
I was curious so I speed up to 70 (max speed on I-90) to check on the truck (I always drive at 60). I couldn't believe when I saw it was a 1 ton truck (Ford 350 or something). I guess that even with a good truck if your trailer is not set up correctly you can have sway. And a lot of it.