@Jonathan Johnson -- Disclosure - I used to work at Nest, and here is my unbiased opinion.
Nest is an incredible product for your personal non-rental home. It is beautiful, energy-efficient, sleek, and secure. It will impress your guests and help save on energy. I highly recommend for your primary residence or vacation home.
However, it is very expensive for a rental home. Isn't your rental an investment? I guarantee that the price vs. satisfaction to the current tenants does not pay off for you. And, you're not the one paying the electricity bill. If you want to get them an energy efficient thermostat, then get them a cheaper one. An investment property is very different from your primary place of residence. And, if your place is cash flowing nicely ... that can change any day when the market turns.
If you are a real estate investor, the ROI is never going to pay off on a Nest (unless you have a Class A+ property that goes for $15k per month ... but those are difficult long-term rentals in the first place to make a profit). Just my thoughts.