Originally Posted by JoeyBike

First - good things about trailers!
1. Like you, hooking up racks to certain bikes is difficult (but almost never impossible).
2. For large riders, getting the weight of gear onto three or four wheels helps prevent breaking the bike.
3. For back-country tours with tons of river crossings/portages, like the Continental Divide route, it is much easier to drop the trailer, carry the bike across, then carry the trailer across, than to jettison four panniers every time, the reattach again and again and again.
4. When you get to camp, drop the trailer in two seconds and use your ATB as it was meant to be used for fun - no luggage or racks. Ride some trails, explore some rutted dirt roads, etc.
5. With a trailer, one bike does it all.
6. Obviously, you can carry bigger stuff, like art canvas and paint kit, easel and a lawn chair ( I met a fellow doing just that on the PCH ).
7. Some trailers are actually lighter than racks and paniers combined.
8. Most importantly, a trailer (especially a two wheeled trailer) will allow your bike to handle almost as if unloaded. This is especially important to folks who stand while climbing and for the occasional break from the saddle.
OK...now the bad news as I have discovered over time.
1. You cannot bunny-hop a trailer. I was flying down HWY 1 in Cali at 50 mph with traffic inches away on my left, sheer drop to death on my right. I rounded a curve and there was a two foot chunk of tarmac MISSING from the edge of the road. On my loaded touring bike I managed to unweight the bike with a small bunny-hop to sail over the hole easily. Had I been hauling a trailer I would be dead. This is extreme, but there will be all sorts of less deadly road hazards that you can easily hop over on two wheels but your trailer will SLAM into them every time. Just riding up a curb can be a menace. Slow down speedy, you'll live longer. You probably shouldn't be going 50 MPH on a loaded touring bike with a sheer drop next to you when you can't see far enough ahead to anticipate road conditions.
2. Due to lower tire pressures on most trailers, they use more of your pedaling energy. So your days may have to be shorter too. There are lots of higher pressure tires you can put on any trailer.
3. Another tube size to carry with you. More tires to go flat. Maybe, but there's not much weight in a trailer and if you use half decent tires you're not likely to have any flats.
4. Two-wheeled trailers will always have their right wheel in the dirt/glass/thorns at the edge of the road. See #3. Most two wheeled trailers are offset to the left, they don't track directly behind you.
5. Two-wheeled trailers make you ride further into traffic. No they don't. See my response to number 4.
6. Two-wheeled trailers and highway rumble strips make you ride completely in the travel lane. No, they don't, see my response to number 5.