This trailer here is what I also have

http://www.cyclelicio.us/2010/burley-travoy/

Is not a nuisance and it's not heavy -- 9lbs. Don't forget that panniers do weight something. If you can do away with panniers, all the better ofcourse. My suggestion to train with a load is due to the load placement of the panniers on road bikes. In order to provide heel clearance on panniers, all these racks have a rear offset from the rear hub. So the load isn't exactly sitting right above the center axis of the rear hub which is what is ideal and what a normal dedicated touring bike will allow you to do. This changes the loading characteristics of a normal bike with an offset rack. With a light load say 10lbs; no problem. 20lbs then yes slightly. 30lbs and up and you will feel it. I use the Travoy trailer sometimes when it makes sense or if I want to carry even more luxury pass 30lbs. I rarely do this nowadays.