Echo that, +/- a pound or two depending on what (or who!) she has eaten recently! And mine looks distinctly like a pit bull!
Echo problems with ADT. I don't have a home security system personally (other than the aforementioned dog) but I have experience with ADT as a member of the property association with my college fraternity. They came in lowest with the bid and did a fairly comprehensive, mostly trouble-free installation about 2 years ago. But since then the service has been less than stellar. I'm instructed to direct everything through my sales rep. but he rarely returns e-mails or calls, and their internal communications is quite poor at present. When I do manage to get ahold of him he says they are "too busy" and everyone "wears many hats" as excuses for the slow service. Join the club, buddy!
I used to work in this business so I so have some insight for you. You might do better to go with a local company that has their fragile reputation to protect, but if you plan on purchasing a monitoring agreement (and what is the service worth without one?) then make sure the local guy subs that out to a national service like UL. I like dealing with local guys but in this business there is a high turn-over rate so make sure you get one that's been in the business for some time and has solid references, the 2 best indicators that they will be around for a while!
You can go the DIY route to be sure, but you probably shouldn't do that until you clearly understand the equipment and its limitations. For instance, motion detectors are very tricky in some applications and can false alarm almost predictably. That's where having experience (i.e., an installer with a bunch of it) comes in handy. At least get 1-2 companies to bid your job first and ask a LOT of questions so you get a better understanding of the options and what might work best for you.
Good luck with it...