After a lot of research comparing different systems, mainly the Alexor and PowerMax, I chose the Simon XT b/c of it's great reviews, easy install, and of course price.
The physical installation of the components was very simple, especially after watching the video. The video is online, not on a DVD as is implied from the photos. The microsensors for the windows/doors just require double sided tape. I also purchased a glass breaker which was easiest installed with double sided tape as well. Finally, the motion detectors were a bit more difficult, but still went up in less than 20 minutes. Read the manual that comes with them b/c they need to be positioned precisely.
I had the panel pre-programmed, so I didn't have to worry about inputting any of the senors. I highly recommend that anyone purchase this add-on. When combined with the fact that it enables you to get the first month of monitoring free (if that option through LiveWatch is purchased) it only costs $10.00. It probably saved me 2 hours of time.
To make for a nice neat installation, I ran 2-conductor wire (that I had to purchase at an addition cost) from the panel down to my basement where I plugged the transformer into the wall. I also ran 4-conductor phone wire to my telco. box and the cord with the 8-pin connector to the basement so that the RJ31X could be mounted out of sight. Finally, I also purchased an ATW indoor siren and turned off (since I don't want any intruders led to my panel) the siren that's emitted from the control panel. I purchased the suggested installation kit with the siren, but found that it wasn't necessary b/c I had already purchased the 2 conductor wire for the transformer and the resistor could have been found at Radio Shack. In the end, the only thing that is on my wall is the control panel, all of the wires are run through the wall down to my basement. I think the photos of the system are a bit misleading b/c the transformer and RJ31X are never shown coming from the panel. There's a lot to be done in order for that reality to come true that is never mentioned.
I'm not totally impressed with the SAW motion detectors. I have them precisely mounted in the corner of 2 different rooms, however, they will not trigger an alarm if I walk along the wall. Yet, if I am in the middle of the room, even 25ft. away, they will cause an alarm. They are simply used as a back up to the microsensors on the windows and doors, so I'm not too worried, plus no intruder is going to walk in the pattern that I have to to avade it.
Another reason why I took a star away is because of the trouble I had making my DSL Internet work nicely with the alarm system. Customer support was great, ultimately, but I was told several different things like buying uneccessary equipment, to make the two different systems work correctly. Utimately, I had to call AT&T to come out to the house to install a DSL Line Splitter at the telco. box.