As long as you wedge them somewhere in the car so that the saddle doesn't slip off they are great. And you can get your bridle, boots, hat etc in the compartment underneath. We use them. They are far far cheaper than Tack Pack's and the like and do just as good a job quite honestly for a fraction of the price.
What we have is an old primary school table, with the table top removed. We push it on its side and stick saddles onto the legs (have foam wrapped round them) and loads of space then for everything else underneath!!! Best thing ever. Have another one attached to tack room wall with bottom two legs for saddles and the top two legs cut short for hanging briddles on!!! Didn't cost a thing!!!
Total waste of money IMHO I have one. I found the saddle slipped off and the whole thing was awkward to carry and heavy when loaded up. However, it makes a great cat bed!
I have one and its fantastic. I do find that the saddle sits better on it without a saddle cloth/ numnah, as it can slip if there's one attached but saddle on it's own is great, plus you can carry your bridle and all other kit in the tray beneath- although yes, it does make a fantastic cat bed according to my youngest feline friend!
I have one which lives permanently in the back of my Land Rover and I wouldn't be without it. My saddle has never slipped off it but I do agree that it would double up nicely as a cat bed as my cats have also tried it out!
I use a small plastic barrel. OH cut an end out of it so can store loads inside and I have taped a non slip rubber material onto the top for the saddle to sit on. I have used it for about 4 years now and no saddle has ever slipped.
I got one of these a few months ago (actually from Blue Pony who were incidentally very good to deal with) and I find it really good. I did try to put two saddles on it on top of each other and the top one slid off so if you have two I would go for a saddle tramp!
I have a pickup with cover on the back so have plenty of room for my tack. However, I have to be organised as I often go to competitions on my own. I pack all my stuff in really tidily (sp?), but by the time I have finished and come to untack and put horsey away the car looks like a bomb has hit it! I got a few of those plastic storage boxes and keep them in the back. In one I keep all the stuff for getting ready (eg boots, bridle number, saddle cloth etc) and the other I keep all the stuff for after (eg cooler rugs, wash down stuff, etc). Then, I just pull the relevant box to the front so everthing is ready.