I've got the Bushtec hide-a-way hitch. Dealer installed it and looks great. I've pulled a Bushtec for years (not real often) and have never had any problems with motor/tranny or anything related. I also believe that those that have problems don't use common sense to keep the rpm up at all times. Many don't even keep the r's up when they don't pull a trailer. Yeah, I know, I heard that the book says you can use 6th gear at 55 mph. (I haven't verified that.) But, you'll hose your bottom end in given time. . . .use common sense here boys when ya pulling a trailer, keep it up!.

I'm fortunate for my dealer knows my riding style. They haven't or even mentioned the use of the trailer as a warranty issue. But they are not afraid to tell you to ride a style that will keep your bike healthy w/trailer in tow.
Also, remember, it's there responsibility to prove that the trailer pulling caused the breakdown/failiar of equipment. But, now you have to balance the cost of your attorney etc... number's might not justify the fight in court. Just my .02 worth. To be honest, with all of the above being told, I only pull the trailer a few times a year when I go camping or......forgive me, going to the golf course..(probably going to regret admitting to that one..but I do love golf)