The difference is that this time we actually have testnets already running the full Proof-of-Stake code, most recent news on this front is that the Ropsten test

The difference is that this time we actually have testnets already running the full Proof-of-Stake code, most recent news on this front is that the Ropsten testnet will merge on June 8th, that's a huge milestone considering Ropsten is like _the_ testnet if you're developing for the EVM, and is only slightly younger than the ETH mainnet itself.