Robinhood is great. I'm hoping they will go forward with a public API, and perhaps allow options trading soon.
1) Doesn't allow limit orders
2) Goes down with even modest spikes in intraday volatility
3) Markets and caters to "uninformed" flow
I imagine they'll only allow long options or impossible-to-break spreads to limit their risks, if they actually go this route (as evidenced by the severely limited margin given with RH Gold).
They certainly allow basic limit orders for buying and selling in my experience, though not the fancier types (conditionals, etc.).