If I missed the run up, I wouldn't buy ETH unless there's upside momentum.
I missed it and I am not worried. I maintain the opinion it will come down eventually.
This kind of a pump always happen with new coins that are well hyped and have the innovation to back it up. It happened with Nxt, Bitshares, etc... (list a million coins here) ...
Also, other coins that already exist have similar technology (Crypti, Qora, etc... eventually RootStock) and a fraction of the market cap... I think equilibrium will eventually be reached.
Neither Ethereum/Crypti/Quora have a killer app as of yet. I think at this point all have an equal chance to thrive if it lands one of the first (or one of the first few) killer apps.
Ethereum does have a better chance at a killer app, but a serious project might be able to make a more successful start up by developing on a less popular chain that is under priced (while investing in it at the same time.)
I think Ethereum is a good cryptocurrency to speculate in, but I think you kind of have to be a bit insane to be buying right now at these prices.