We've traveled nearly 6,000 miles towing our VW Tiguan on a flatbed car trailer. At nearly 32' long on the motorhome alone, when we add the trailer, we're just about 54' long.
In all our travels, we have only had to disconnect the trailer once before backing into this particular campsite. We might have been able to just back in and nose the motorhome up to the edge of the site, but it was a dark, rainy night when we arrived and the back edge of the site had a downhill slope. It was just a smarter choice to disconnect in the rain.
Like you, we can't tow 4 down, or even 2 down on a dolly due to the 4Motion system in our VW. For us, the car trailer was a great choice as it's under the towing limit of our VW, so we can use it for other things like trips to the dump, the Big Orange store and more.
I will say that in all of our travels, people towing like us are few and far between. Certainly the most common two setups are 4-down and 2-down dollys, but we also have the advantage of being able to backup with the trailer attached. Can't do that with a 4-down or dolly.
This has proven to be convenient in our travels, as well as a trip we took to one campground where our non-RV Nagivation routed us on a path we could not take -
A day of travel …and backing up! | Our RV Journey
As far as loading the car up and down from the trailer, I've got that down to about 10 minutes. Not that much more time than it takes any other TOWD setup. Since the car always sits in the same location, I know where to setup the ramps and where to stop on the trailer. We use 10,000 LB straps on each wheel, and due to our rim type, I just strap them right through the rim. While I could also run the straps around each wheel - like a wheel net tie down, I'm more comfortable with going through the wheel. I do think that I'll buy a set of wheel nets, and give them a try sometime in the future.
I'll usually get the car nice and tight on the trailer, lock and wrap the excess strap length, and then stop for a quick "pull check" before we get on the highway. I also make sure that I do a pull check every time we stop and get out - this is usually no more than a couple hundred miles at a time.
Another thing I like about pulling the trailer is that it is a good, easy visual indicator to keep me in our lane. I check my mirrors on a regular basis while driving, and especially on narrow roads, using the car trailer as a lane guide works out really well.
The downside to the car trailer, obviously the extra weight we are pulling. With the trailer and the VW we are a few hundred lbs under our max towing weight of 5,000 LBS - I calculated all our weights before we bought the RV and the trailer as I was also looking at an aluminum trailer that for about twice the price I paid for our wood topped one, was only about 500lbs less - so we decided to put that extra money into the RV fuel tank ;-)
I think our trailer is about 1,300 LBS, so we probably lose a little bit in fuel mileage with that extra weight, although with the trailer and car we are still getting between 6-7 MPG - usually more towards the low to mid 6 range.
Another advantage I like with our setup is 4 wheel electric brakes. We run a Tekonsha P-3 Trailer Brake Controller in the motorhome and the braking performance is really great.
Here's what we look like when towing
While Tandem Dolly's look very versatile...why do you all think they are called a "tandem dolly" 
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