A few years ago a coworker asked if I wanted a free trailer. Well, sure.... what's the catch? Had to take the camper that was on it.
Went to his house, and the trailer was made from a 1/2 ton long bed Ford 4x4. On it was a really sad looking camper. The corners were separating, and the interior was nasty from roof leaks. A relative of his was living in the trailer at the beach, and the salt spray really ate up the aluminum.
I hooked it up and asked where the nearest dump was. Drove there and two large forklifts pierced the sides, lifted it up, and I drove the trailer out from under it. A huge-by-large bucket loader came and flattened it with its bucket, then shoved it into the pit.
Because I had to pay by weight, I remember the before and after weight showed the trailer was just over 1000 lbs. I don't recall the exact weight now, but that's a fairly good figure for a full size pickup trailer, in the 1000 to 1200 lb range. (The camper that was on it was almost 2000 lbs, probably because all of the wood was waterlogged.)
The trailer tracks OK. It has a fairly long tongue on it, which helps with tracking and backing up. Short tongues can sometimes have tracking issues, and react quickly when backing and turning. You have power steering, so that's less of a problem, but with manual steering I've found a short tongue sometimes veers so fast that I can't correct for it fast enough with manual steering.
I have yet to pull the pinion out of the pumpkin. Need to make a blank plate, and other priorities keep putting it off. It would probably increase my gas mileage when towing by a whopping 1 or maybe even 2 mpg. I don't know if this amount of friction helps with tracking or not.
One consideration with pickup trailers is just how much load they can carry, as well as their legal load. In Oregon, utility trailers do not require a title or registration if the gross weight does not exceed 1800 lbs. Since the rule of thumb is that a pickup trailer weighs about 1000 lbs, that only leaves a legal 800 lb load. The design limit of this trailer is 1000 lbs, since it's made from a half ton pickup. I've put in a half a yard of gravel, which is about 1400 lbs. The springs start squatting quite a bit.
Another consideration is tires. Few people invest the money to put proper trailer tires on trailers, especially trailers made from pickups. Running cheap tires can get you into trouble if the load rating does not meet or exceed half of the gross weight. Because my trailer was 1000 lbs, and a half yard of gravel is 1400 lbs, that means that the tires must be load rated for 2400 lbs divided by 2, or 1200 lbs each, plus it's a good idea to add 50% overload rating. Total is each tire should support 1800 lbs. The crappy tires that were on it were only rated at 1500 lbs each. The trailer tires I put on were rated at 3000 lbs each, which was overkill, but that was a typical rating for them. Trailer tires are also designed different from vehicle tires. Not only are they designed to have less rolling resistance, but the sidewalls do not flex as much. This means there is less oscillation of the trailer at high speeds. Trailer tires aren't cheap, though, so if you run vehicle tires, make sure the load rating is more than adequate.
The best donor trucks for trailers are 3/4 and 1 ton, not half ton. Not only can they carry more payload, it's easier to convert them, at least from the standpoint of the axle. Simply pull the axle shafts out. But the fact is there are more half tonners than heavier trucks, so those will be the most common pickup trailers.
As for off roading with it, I've driven it off road at my mother in law's ranch, but only to get to the burn piles or dump pit. It's on the heavy side. From a size viewpoint, it's like driving a half-ton pickup for width, only you don't care about body work damage (at least I don't). This is why I have a pair of jeep trailers. One is a civilian trailer with tailgate, and it's my utility trailer. The other is a military trailer without tailgate, and we use it for camping. Much easier to take off road, though their cargo capacity is only 500 lbs off road.
Have one of those too! 
