Too often a product just don't cut it, much less live up to the hype. In this case, this product meets or exceeds all claims.The installation guide is very well written, illustrated, and the type font does't require a magnifying glass to be able to be read easily. It is easy to mount in the same space as the old unit because the opening for the wire in the backing plate is not only large enough to accommodate the wires, it allows you to move the mounting plate to "center it" exactly where you want it. It requires only two screws and the mounting holes are elongated enough to allow you to adjust the mounting plate on the wall to get it nice and level. If your current thermostat has four wires and the wiring colors conform to standard practice, it is nearly impossible to screw up the wiring job. Just remember to make sure the exposed wire ends are straightened without cracking the wire and that you brighten up the ends of the wire (clean the copper) by using some very fine steel wool. (you did turn off the power at the breaker box, right??). When the wiring is done, you load the batteries in the battery compartment and attach the control panel to the backing plate. Again, the instructions are clear and the holes and sockets actually line up. Easy! Then you put down the installation guide, pick up the operating manual, turn the power back on, and follow the very clear directions to set up your heating and cooling schedule..Very easy.A couple of nits to pick that caused me to only rate this 4 stars. NIT #1: Honeywell provides a small "pull up" operating guide with a small exposed tab that's supposed to fit between the backing plate and the control panel. This saves you a trip to file cabinet or drawer when you need to change your settings. In my package, the "pull up" guide was much larger than shown in the illustration and the space provided for it the thermostat housing. Not a big deal but a bit annoying since it would be handy.NIT #2: The control panel screen has a back light when greatly improves the readability of the screen print when you begin to program the unit or change settings. It times out rather quickly, in my opinion, which can really hamper seeing the menu and selections. There may be a way to program the timer but I couldn't find it. If you're working in a dark area, a small LED flashlight will come in very handy. Having a "headlight headband" is even better.