I'm going 64gb. I don't know if I will need it. In fact I doubt I will. But I do game occasionally and if this takes off as that sort of device, that might chew through my storage space.
But I'm not sure. I will probably end up buying two of them or at least buying next generation and kick this generation from the living room to the bedroom. I know I won't need full storage in both versions. So I could go 32gb with the expectation that before that becomes a constraining issue this device will get relegated to a less used TV.