I just bought the 550 myself and plan to install it over the weekend if time allows.
(I was certified as an installer although I never actually DID any installs... So I know but don't have a lot of experience....
Looks to be a nice alarm...
For about $100 you can add 6 more channels.
I THINK you get a different remote with it too... (May be less...)
In my cavalier I used Cliffords Smart Windows on its two windows. I used them because the SW unit would handle all the difficulties of making sure the window didn't catch anybody unaware.
If setup normally it would roll the windows up when the alarm was armed. The convienience factor was that you had one touch up AND down with the unit. And if you had an output hooked to the SW unit if you pushed the button within a few seconds of arming the alarm you could 'vent' the window. I think it also had if you hit the button again it would go down all the way...
I disregarded the normal alarm settings and wired relays to the window switch wiring. It ended up using 2 outputs of my remote since I had both windows wired up in parallel.
One button would roll both windows up and the other would roll them both down. Worked quite well actually. Other then the fact that the relays couldn't always trigger the one touch up and down feature. Was REAL fun playing with the windows in a crowded parking lot though.
I also had cliffords "sense and tell" module as well which was a radar unit. It would detect your presense and warn you away with a voice.
Pretty cool except RF would set it off..
I had those modules wired to a Code Alarm Elite Competition alarm.
I will probably be yanking the code alarm in favor of the viper 550 with a couple extra modules...