Trane is also a popular one. As is Venstar.
I was on Venstar and ended up replacing the Insteon module every year or 15 months and it was really getting under my skin. That and I don't like white plastic things on my walls because in time they yellow. I made the leap to Nest for the aesthetics (because I knew Indigo would still be controlling it so I didn't need the smart features). I don't know if I would go this route again or not.
Pros: The Nest is really pretty. I mean if you are after aesthetics then I think the Nest is a hands-down winner. It works and is quite intuitive and responsive. By itself I would go with the Nest over any thermostat on the market because it does everything they do plus is pretty.
Cons: Internet controlled - I don't like that my Indigo requests have to go to the Internet to change a setting and then come back down to the device. More than once the Internet has gone out and my automatic schedule to warm the house didn't kick in and I got up to a very cold house and had to wait fo it to warm. I feel the same about anything Internet connected these days and the Nest has gone a long way of making me jaded about it. Now the Nest is smart enough to keep a copy of your schedule locally so if you want to get around this then you could have a back up schedule that would kick in even without the Internet. The other thing I don't like: It's a Google product and, as such, I know they are collecting every ounce of data from that Nest for my "dossier"
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There's my take. Lots of folks love the Trane and it's a really cool looking "techie" device that seems to work well. I wish my Nest were all local, then there just wouldn't be any discussion in my mind.