Does any one have a motorcycle carrier like one of these http://www.discountramps.com/motorcycle_carrier.htm. If so how well do they work? Do they work on a car if you have a trailer hitch? What are the advantages/disadvantages of these compared to a small trailer? Thanks.

I don't know about this brand of carrier but I do use a carrier sometimes and they work well. Most if not all of these carriers require a class III hitch. Lots of trucks and suv's and full size vans have class III hitch's but I don't know of a car that you can get a class III hitch for most cars use class I & II hitch's. They do save gas over pulling a trailer.

I built a carrier like this to carry my bike and it works great, but i have a feeling it would bottom out the suspension on a car. I use mine on a minivan and it still almost bottoms the rear shocks.

I have one that will hold two bikes. Works fine, just make sure you tighten down the suspension on the bike(s). Mine goes on a F-150, would be too much for a car suspension.

Dan12,
I purchased the single bike carrier and its very well made and sturdy and works great. I mounted it to my trailer hitch and its very secure.I would invest in the hitch lock for security purposes.Very good product.

The model I have is the AMC-400, aluminum.

We have one and it works and holds the bike but the whole things wobbles a little bit... But not much the bike wont fall out or nothing... I dont know about the car question we have an avalanche...

You need to check the manual of your car to see what the max tounge weight is...obviously its nowhere close to the towing capacity because it doesnt distribute the weight....your manual should tell you, or it might even say on the hitch itself (if the hitch is stock)

I have a single bike carrier and it works great.
adv: way cheaper, dont need to worry about tires, electrical, maintenance, liscensing, takes less space in the garage, lighter, easy to move around, etc etc
disadv: very limited in what it carries, harder to load a bike with a single person, (on an SUV you cant open the rear doors, car should be fine with the trunk), youll need a better suspension to use one and most likely a car wont do it.

I was thinking about getting one of these but I can't get over the thought that it's just unsafe. For those of you who have it, just how tight does the bike feel on there once it's all strapped down?

Its safe. Use rachiting straps and have somebody jump onto it to get it as tight as possible.
You can also get suspension savers so you dont have to pressurize the forks when tightening it. I dont have them but people have suggested them.
My carrier is only made for one strap from each handlebar, but I use at least 4 straps ever time. One on the back tire, each side of the handlebars, and one straight down from the frame.
No problems so far. Get it nice and tight and it wont go anywhere.