The Ethereum releases of Frontier, Homestead, Metropolis and Serenity.

The Ethereum release process has seen the usual delays - as of course it's software and never going to be ready on time - as there are always going to be be multiple unknowns that aren't factored into the build. This is especially true of such an ambitious build as Ethereum.

Also with the ethereum launch process there have been numerous changes of plan that have led to a myriad of conflicting reports that are still out there as to exactly the roadmap is. The blocktime was changes, the block reward was changed and a few other key planned developments were kicked down the road.

Again this is all to be expected as that is the nature of development. The other mitigating factor is that after raising money in Bitcoin from the ether crowdsale, there was a huge drop in price - and rumours of rather liberal distributions of cash instead of budgetry discipline by the Ethereum foundation. This led to the foundation having to cut costs and send of their programmers to run their own projects build on the ethereum blockchain. this has doubled the time the ethereum foundations cash reserves will last.

So what are the key phases:

Frontier

Frontier was the initial release of the ethereum network pushed live in July 2015. It was a bare bones release planning to allow the more technically minded to release their own apps, allow people to mine, and get exchanges up and running.

Homestead

Homestead was planned to be released after a month of frontier going live as a best case scenario. As of January 2016 the Homestead release is about 80% complete - but the goals have been altered somewhat as frontier took in a large part of its projected development pipeline - for example the block reward was set to the full 5 ether.

In its new form Homestead has become more of a patch work of fixes to remove the risk warning attached to the ethereum homepage!

Metropolis

Metropolis is the release that opens the gates to the masses. This is where there are fully fledged and tested user interfaces for the non technical users. Although this is now being performed by individuals - for example the ethereum desktop wallet. Again it is unclear when this phase will take place and whether it depends on the pace of external community development.

Serenity

Serenity is the last phase and has one key principle - to switch the ethereum network from proof of work to proof of stake - essentially reducing the power consumption of the ethereum network. When this is going to take place and under what conditions is of course anyone's guess - although it is thought to be in the planning for the start of 2017.