I've had my system for over a year and am very happy with it.
I have had a few false alarms which were totally my fault; they call before they contact the police and they always called within 1-3 minutes.
Installation is easy and wireless. The system can be configured on your computer. The battery life of the components is very good. Monitoring is very inexpensive.
Be sure to go to simplisafe.com/mark to save 10% off your purchase. Once again that's simplisafe.com/mark. I listen to too much talk while at work on midnights. I could hear his promotion as I was reading your question.
We've had our system for a couple of months now. Very easy to install and set up. It's cheap to set up as a monitored system or you can just make it a local alarm if you don't want to pay a monthly fee.
I bought our system as a re-furbished system; saved some money. It had a three year warranty, same as a new system.
I had a problem with one of the key fob controllers after about a year. I called the customer service number and they immediately sent me a replacement, no problem.
Another nice feature, you have an online account if you set up monitoring and it shows an event log of the weekly test to make sure your system is communicating with the monitoring company and every time your system was armed and disarmed and who did it. It seems to store this forever.
I did exactly what you did Doug. I figured re-furbished meant they tested it before it shipped? Using it exclusively for a vault room. Everything else I have is just crap!!
We've had the system for 4 yrs and been happy with it. Motion sensers and indoor kitties are a no go, obviously. Response time has been good. Problems seem to be easy to fix. Sensors easy to add or replace.