Check their fees. After long being frustrated with the poor performance of our Roth, and the extremely high fees, I decided to handle our own. Chances are, if you just invest in an index fund, and account for the fees a manager charges, you'll beat them handily. Check out the math.
Their pricing seems to be fairly straightforward - about a dollar fee per month per $5k invested, just that one fee based on your balance. Seems almost too simple. Betterment looks very interesting. I would love to build some wealth as soon as possible. I'm in a good position to do so, as I'm on track to have zero student debt and a bit of savings. The only big problem that's keeping me from attempting something like Betterment is my utter lack of financial knowledge, especially taxes.