Assuming you have the wiring in place, it was the easiest install I've ever done. Super easy to drop on your network too.
As previously mentioned, no service charges.
We like ours, use it a LOT, had it for over a year.
Never really did the whole "learning" thing, but the interface (web and phone) for setting up your schedule is nice, and I particularly like the fact that I can control/monitor the temp in the house from pretty much any place on the planet with a network/phone connection.
Also of note, they will send you a monthly email comparing your energy usage and let you know how it compares to previous months.
I have also been looking at their smoke/carbon monoxide detectors, the price is a little steep, but have been considering it for our son's room.
I have one with a traditional HVAC (air conditioner and gas furnace) and it works great. There is no monthly subscription or reoccurring costs associated with the device.