I have a self-installed alarm system (in an existing structure - not new construction) that is tied into a larger home automation system. I hardwired all the doors, but ended up using wireless for most of the windows. While I could have hardwired most of the windows, I didn't want to have to run all the wires and take trim off the windows and reinstall, touchup paint, etc. The wireless actually works well and the batteries last years in these devices. In the end, a good security system is multilayered, so door and window contacts are just the first line of defense. You also need glass breaks and motion detectors to add to the total effectiveness of the system. Most alarms have "two-way" wireless systems so the alarm does monitor the wireless zones. If a wireless device drops off the system, it alerts you and/or sets the alarm off. This is really about as secure as hardwiring zones. The biggest difference between wireless and hardwired is the cost. A hardwired sensor might cost $2-$5 each while a wireless sensor might be $20-$50 each.
We use the alarm status to trigger all sorts of other automation tasks (like changing HVAC setpoints, turning lights on/off, turning A/V equipment off when armed, etc, etc, etc). This is very helpful because things don't change based on a set schedule, but on our family's actual activities. For example, if we stay up watching TV later than normal, the HVAC system doesn't change it's temperature settings until we arm the system to "night" mode. Or if we are going to be away from the house for a few days, we arm the system "Away Vacation" and it set things differently than it would if we just leave to go to work.
The last thing I would recommend is for someone to use ADT or any other company that provides a free system and installation and then requires that you enter a contract to pay them monthly to monitor the system. They obviously make their money by overcharging on the monitoring service. IMHO it's like leasing a car or renting a house. You will end up paying a whole lot more than paying a local installer (or even better DIYing it yourself) to come install a system and then have the freedom to choose whatever service provider you want. There are several reputable companies (like Alarm Relay) that provide monitoring services for reasonable prices without any contracts.