Excellent question… We must be several hundreds (thousands) of SmartThings early adopters looking for such an alternative.
The problem is that “the devil is in the details”, and that to reach the 99.999% reliability level needed for trouble free Home Automation, you need to take care almost of ALL the details, WHEREVER they are in the chain.
And then there is the price vs functionality issue…
The bottom line is that you will NOT know a home automation will work adequately for your specific needs until you have “played” with it multiple months, AND on a large enough scale : the error rate which is acceptable when you have only a few Devices could very well be UNacceptable when you move to several dozens of them !.. as I did learned painfully 
.
The tentative and partial conclusion I have reached at this time is that a 99.999% reliable system is likely INcompatible with a too open, too young, cloud based, system… unless the same company controls all the components along the way, either Hubs, Devices or cloud. And even in that case, you will have all the vagaries of Internet TC/IP connections, a technology designed more than 30 years ago by the Pentagon in a “fire and forget”, “let’s survive the next nuclear war” spirit…
At that point, for local operations, I would likely recommend FIBARO, which has strongly impressed me with the great engineering quality of its products.
And for a cloud based solution, I would look into Apple’s HomeKit, although they are currently very limited in number and type of devices supported; but that will improve in the next 12 months.
In the meantime, as long as you do not require high reliability, SmartThings has a reasonable price to “play” with Home Automation… and learn yourself, the hard way, all its present limitations.
But do not build anything “mission critical” on top of that, that would be like building a skyscraper on top of a quagmire…