Ethereum has been described by core developers as oil to Bitcoin's gold. it is similar to other metacoins in that it acts as superlayer that empowers the blockchain, that is something like when Javascript was added onto HTML.
It empowers an immense number of custom applications on top of the blockchain, for purposes as diverse as contracts, derivatives, custom currencies, and filesharing. As Robert Ver said recently in Miami, if it works it is at least as innovative as Bitcoin itself.
Enthusiasm is high because, unlike Bitcoin, there is immediate use value for ether within the Ethereum network. All of the applications built in ethereum consume amounts of ether along with their computational cycles.
For folks looking at things from a macroeconomic standpoint, this makes Ethereum perhaps the most interesting of the new cryptocurrencies, because among other things. there is immediate use value for ether outside of trading, mining, and the other standard features of the first generation of cryptocurrencies.
Is it Bitcoin 2.0? Time will tell.