I have a bunch of Z-wave products in my house and I really like it. I use a Honeywell thermostat with my system because it interfaces with the Z wave stuff. Would have bought a Nest, but again its not compatible. The only advice I would give is avoid the locks that are fully mechanical. They are battery killers. I ended up removing it and going back to an older version with Z-wave.
As for monitored alarm, I only have that set up since my house insurance discount cancels it out. Otherwise, its pretty useless, if someone wants to enter your home, they will. They only need a minute or two to do what they want before anyone shows up. The best security is good neighbors.