I have installed alarms for several years actually, but have not put one in my z yet..not sure why not but it is coming soon.
I would only put in a DEI brand alarm. This includes a great variety, including Viper, Clifford, etcc..
I was originally going to put in the 790xv, but DEI has recently released some new stuff, such as satallite alarms, which allows you to track your car on the internet (good if your car gets stolen) and alarms with turbo timers on them.
I will definitely get one with a remote start.. stay tuned as I decide which one to go with. I will also do a detailed HOW-TO.