We've been doing the truck camper thing for ~6 years now.
First, staying at the track beats the hell out of staying at a hotel for a race weekend. While everyone else is trying to pack up for the night, you're grilling your dinner enjoying a frosty beverage. And in the morning, having a nice cup of coffee while everyone else is rolling in and unpacking again. Not all tracks will allow you to camp (usually city/county regs), but where you can, it's great.
Our decision to go truck camper was based on a lot of research. Truck campers are comparatively expensive, but have some advantages. No separate drivetrain to maintain, no registration/insurance (taken care of by the truck), fairly small footprint for storage, and when mounted, the RV has a fairly small footprint, so you can go places you couldn't get with a motorhome or camp trailer. I also looked at living quarters trailers, and they were even more expensive, and to have any decent room (where you're not sleeping in the garage), you're gonna end up with a 40' gooseneck. The work/play stuff is cool, but if you want to put the car in the trailer overnight (rain, etc), you're out of a place to sleep.
The other advantage is it's just a camper if you want to use it for something else, and you can still tow behind it. And when it's not mounted, you have a truck to do truck things.
There are some disadvantages... there's not a ton of space in a truck camper. Ours has a single slide, which makes a huge difference. Ours also has a wet bath (the whole bathroom is the shower), which is a PITA. I would recommend a dry bath if you can do it. For two people and a dog, we're fine, but for longer trips (more than 1-2wks) it's a little cramped. For two + kids, it's gonna be tight. Make the kids sleep in the trailer...
The other issue is truck campers are HEAVY. Ours is ~4300lbs wet (loaded and full H2O tank). You read that right... it's two Miatas. Once you start adding things like generators and slide outs, they get heavy fast. Most SRW trucks are going to be overloaded with any of the larger truck campers.
I recommend looking at this site to figure out axle/cargo weights: http://www.visualsc.com/tc_calc.htm
The other issue is cost... truck campers are expensive for what they are. When we bought our camper, we bought used (9 years old), at about 1/2 original MSRP. Fortunately, many RVs don't get used much, so it's easy to find them in nice condition. Or at least it was 6 years ago.
Overall, we're very happy with our setup, and it has provided us with many adventures.
All that said, we're retiring within the next year, and now looking at motorhomes because we want to increase our traveling time, and would like more room for spending a couple of months on the road at a time. The good news is our camper is holding it's value very well.