Hi there,
A bike trailer is useful if one needs to go on a self supported tour where food and water are not available for days at a time; something like the Australian Outback. It's also nice to distribute your weight but if you plan to tour in places where you don't need to haul 30 liters of water with you, I don't think you need it. The extra weight of the Yak is not worth it for "solo touring". I use my BOB yak when I go on short camping trips with my wife. She doesn't have a touring bike, so I carry everything. The BOB Yak is great to fit a 12 pack of beer, food and the camping gear. Otherwise, I don't use it. I'm going on a small tour (8 days) next week and I was thinking of bringing the Yak with me but after a week of full loaded tests around my city, I decided to cut down on many things and leave the trailer home. It's your choice. For me, the trailer is no big deal once on the open road, but navigating it around big cities, elevators, subways, is impossible. Also uphill is no fun either.