Make sure to check with your local utilities for rebates. I purchased one of these over a year ago and got $100 back from Eversource. Not too shabby 
They told me I could hack it for more feature but after hacking it a few times with my cleaver it just stopped working.
What do you get when you hack it? Are there additional features or something?
Correct, I got two of these (Nest E) from Commonwealth Edison in IL. First one was $39 with instant rebate, second one $69 with instant rebate but they tossed in a Google Home Mini for free.
Also, these work better or let’s say more reliable, if you have a C wire they but do work with a 4 wire setup as well.
I picked up one of these here on Woot back in 2018 for $120. After a $75 rebate from my local energy provider I think it was about $45 out of pocket.
I did need to run a new wire from the thermostat to the furnace (4 to 5 wire setup), but that was super simple due to my open access basement and cost about $10 on amazon for the wire.
I’m pretty happy with it. Easily programmed online for temperature and the ability to control with my phone or Alexa is nice. Easily the best feature we use is the automatic timer fan, really helps to even out the temps in our home by running the fan every hour for a few minutes, especially in winter when one side of the house gets warm (or even hot) due to the sun and the rest is cooler.
Had a couple of these and they work really well as long as you don’t have 2-stages or more. I didn’t realize that you could use these for 2-stage as long as it wasn’t 2-stage heating and cooling. Which still doesn’t help me because the new Tranes I had installed a month ago are apparently 2-stages on both. Hence, two thermostats plus sensors I can no longer use. 
They also didn’t want me to get the Nest Learning Thermostats (which should handle my kind of HVAC) because I would lose some functionality over the Trane smart thermostats. They actually work well, but they don’t allow for extra temperature sensors to control the thermostat which sucks when the room the thermostat is in is either the warmest or coolest room in the house.
Got 2 from Ameren in Illinois for $39 a piece. Depending on your set up, they are pretty versatile. I was able to get one hooked up with an old gas boiler with 2 wires. Works fine heat only.
I tried one of these last year. I wanted to like it but it constantly read 5-8 degrees warmer than the house actually was so it was running the AC longer than it should to try to cool the house making the house freezing. Every other thermometer in the house and the previous thermostat all agreed with each other. There is no way to calibrate this thermostat. Talked to Nest support and they sent another unit and it did the same thing. Both went back. At the time I was able to find other reviews stating similar issues. I’ll try another brand someday.
I have two of these. One upstairs and one down. They work well and do their job. They can be adjusted to the tenth of a degree (or maybe more), but it only shows the full degree on the app and device. So that could be more accurate. But the app works well, they seem to have good enough wifi range and are connected 99% of the time. They also look nice without looking cheap like I think they do in the stock photos.
I got them from my utility company. Paid about this, or maybe less, for two of these and they each came with a google home mini. So this may not be the best deal, sorry Woot.