I like them.
I was going to get one for the subaru, but then I thought about it.
Imagine this, you are driving down the highway and see the left lane is open. It's a nice day and you feel like opening up the throttle a bit, ( we all do once in awhile, that's why we mod cars), you get in the left lane and do a quick pull, maybe you pass a couple people on your right. But, one of those people is in a bad mood that day and you really just tripped them off and lit their fuse for whatever reason. Now, they are gonna take their anger out on you, so they pick up their phone and call those three magic numbers. Since you have a personalized plate, (most of them are very easy to memorize), you have a very big target on you, now that the police know what they are looking for ( a grey grand prix with "xxxxxx" plate). Now, while the police cannot prove that you did anything, if you get pulled over while still around that other person who called, that person is going to make your life a living hell for that part of your day.
Sorry for the story, but with how much I like them, and the fact that I hang out with the "local scene", I am easy to find now.
So, in conclusion, it is all your choice what to do. If you really want one, then get one. I am just saying realize what can happen if you pass that one person who spilled their coffee driving to work. lol