ADT runs specials all the time, the thing to check are the installers,, make sure they are professional. Some installers are nothing more than kids that did car stereos in high school, they can be sloppy.
Motion sensors are fine with NO pets or children, also have them zoned, if you get up to use the bathroom at 3:42 a.m. you don't want it going off either..Most can be isolated to areas your not going to use at bedtime.
Check for system integrity if the power goes out, and for how long with battery back up, they need to tap into your residential phone line, what happens if the phone line is cut?
Also check with false alarms in you local police dept. Some will CHARGE you if your not home, and the alarm goes off, etc,...
Read the fine print. Some will give you an introductory monitoring fee for a year and than "bump" it up after the promo.
and Watch Rob's DVD and let us know how it goes...