I have a trailer tent and love it!
There are good and bad points about it though, i'll try and summarise.
Its got two decent comfy double beds raised off the ground. We have camped when its been really cold outside and never felt cold at night. Its night and day to sleeping on an airbed.
The trailer part of the tent is really easy to assemble, it is quite heavy but you only need to open up both sides and thats it assembled really.
The awning part is massive, about 4 metres by 3, so there is plenty space for a table and chairs and a cooking area. The awning bit did need a bit of practice, but essentially you put the poles together and pull the canvas over, after a few attempts its pretty easy.
The ground sheet is not attached to the sides, so you can get insects in the awning area.
The canvas is really waterproof, however if you are unlucky enough to have to pack up in the rain you have to dry the canvas out (but you need to do that with any tent).
Once we arrive home we put the trailer in the garage and thats it, none of this emptying the car and putting all the camping stuff away.
We have 4 children so going camping in one car is always going to involve some sort of trailer anyway. We bought ours (a raclet marathon) from ebay for £500.