I just finished up with replacing a Concord 4 Ultra system, with a Honeywell Vista 20P. Let's just say it was a learning experience, as I have a lot of sensors. I am very pleased with how it turned out, almost everything works, and works well.
If you have wireless sensors on the Concord 4, you can get an older wireless translator cheaply on eBay. Note however, that a Honeywell system does not learn sensors the same way as the Concord. Tripping the tamper switch will work, but that uses a different loop number than what is normally used. This presents problems with wireless smoke and glass break detectors if you try to use these on a Honeywell system.
One major problem I encountered was I had to cover all my motion sensors while doing the learn process in the Vista panel. If I didn't, each time I walked past one, it would pick that up instead of the one I wanted, like a door switch.
I like that fact that I now have IP monitoring that's free now. Eyez-On provides this service via their EVL-4 module that so far works flawlessly.
I don't have the Tuxedo Touch keypad yet, but that's planned for the future. It gives you the ability to view cameras, and integrate Z-Wave into the system. Still researching how well this will work, as it is quite expensive. It also gives you wifi connectivy if you are big into home automation, and don't use Z-Wave.
Feel free to ask questions, but do your research. I have spent a little less than $300 so far on the project, and it is turning out very well.
