We're heavily insulated and don't even run the AC on 100 degree days.
I'd be far more interested in automating the combination of our whole-house-fan + windows/shades.
Meanwhile, an un-smart thermostat with a timer can be had at Home Depot for $25, and will achieve 80-90% of the savings assuming you have a typical schedule.
On the downside, the Ecobee doesn't "feel" as high quality. The touchscreen shows finger prints, it has a plasticy feel and you don't have that nice orange or blue background color indicating whether it's cooling or heating (not a big deal). It also doesn't have the schedule learning system, but to be honest I would usually adjust the temps manually throughout the day anyway. It also doesn't have the automatic fan function after the AC has run, sort of an afterrun fan which helped continue to cool the house without the AC on.
In the end I wanted to try something different and so far I think it's met/exceeded my expectations. Just hope you have a C wire when you install! :)
1) Vacations: with the Ecobee, tell it when you'll be away (date/time range) and it will go into vacation mode. I travel often and I can add multiple vacations in advance. Not a complex feature and surprising Nest doesn't have this. With the Nest I have to keep tweaking my Away mode temps to ensure that it warms up when I return and doesn't just switch back to Away and stop heating (it can take hours to go from 50=>70 when its 15 outside).
2) Learning with the Nest was always wrong for me because I have an irregular schedule so I turned that off. For me, that was originally an appeal of the Nest.
3) Ecobee multi-room sensors are awesome. Unfortunately I've learned that my office is always 10 degrees warmer/cooler in summer/winter.
4) Ecobee is HomeKit/Siri compatible which I haven't really used much.
I installed the Ecobee myself and had to install the little box on my furnace to provide power. Not ideal, but easy.
Most don't touch it.
Disclaimer: I work there.