I've done some touring with the 2-wheel Bike Friday trailer since it lets me take along the suitcase that serves as the bike box on flights to/from the tour. I do notice the little tugs and pushes when the trailer goes over bumps in the road. Not really objectionable, but it took a little getting used to at first. I prefer to use panniers for most touring mainly to reduce the total weight of the load. I try to keep the weight of my luggage down to 20 lbs. and using a trailer adds considerably to that. The added weight certainly makes itself known on extended hills.

A trailer would probably be more suitable when carrying heavier loads - and I do use one whenever I want to tow one of my boats.