I'm have a Clifford Concept 600 installed.
Seems to work o.k., but the 'car-jack' option really is a pain in the ..........
You can disable it though, but why bother with such a option, when you probably better off with a cheaper alarm from clifford.
Personally i wouldn't go for the very expensive alarms, since if they want your car, they'll have it, no matter what alarm you have.
Here in Holland they have this "SCM-approved" label on some alarms (goverment thingy), which show on your window (little triangled sticker). I do know that car thiefs leave the car alone if it has one of these stuck on.
Clifford makes very good alarms. The car-jacking option is a pain, but you get use to it and it not that bad. I had it on mine and I liked it after a week or so of playing with it.
One thing to tell the installer. Don't have them place the alarm light on the black panel to the right of the clock. The installer put my light there, and I later found out that you have to purchase the entire clock to get that black panel (part of clock assembly and does not come off). I wanted to keep my alarm and transfer it to my new car (alarm guy only charges $25 to remove), but instead I had to sell it with the car.