I've hodled ETH since about $20 so I'm very reluctant to see my whole stack. I have however, moved a significant amount of profit out of ETH in to Litecoin, see my reasons here: https://steemit.com/cryptocurrency/@jhcooper7/my-cryptfolio-investment-why-i-diversified-profits-from-ethereum-to-litecoin

Personally, I think that whilst ETH has some problems the flash crash was not one. That was simply a cascade of longs being called on a single exchange, it could have happened to any crypto and it just happened to be ETH. I'm not basing any investment decisions off of that. As for the inability to scale holding it back, just look at Bitcoin. I also saw something recently from Vitalik saying that he was aware of the pressure ICOs were creating on the network and he was going to find a solution. This man is smart, if there's a solution you can bet he can find it pretty quickly.

The main issue is that few cryptos have the capacity to scale right now, it's too early in the game for them. Those that do don't seem to be tested. However, ETH has a load of great releases over the next few months/year. Between Casper, Metropolis and Sharding I struggle to see there being many other safe options.