Rich,
Sounds like you got a good basic system. I'd spring for a glassbreak detector though...usually if someone is going to break in, they'll smash a window and then MAYBE reach in and open it to crawl through. A good glassbreak will listen for TWO specific frequencies in order for them to trip- first, a very low frequency or increase in pressure as the glass flexes before it breaks, and then a high frequency when the glass actually shatters....keeps false alarms to a minimum.
Hardwired sensors are a good way to go as long as the installer has a bit of experience running wires. Wireless devices have come a long way, most (if not all) use some type of lithium battery that will last for years before they need replacing. I've seen some last as long as 8 years on the ITI (now GE) systems. Also, most modern alarms that support wireless devices have a jam-detection feature that can be enabled.
You might want to consider a cell-backup too. The alarm panels that ADT uses are made by Honeywell, who make a nifty little cell unit that's only a couple hundred bucks or so. Nice to have in case your potential intruder comes equipped with a pair of wire snips for the phone line.
Anywho, sounds like you already have a good sense of the situation. Alarms are nice to have, but certainly not as effective as common sense and a well-placed slug of lead <img src="/forums/images/graemlins/smile.gif" alt="" />