Hello GreenMan,
there are as much alternatives as customer... some of our customers move to Office365 in the cloud and a lot using the Exchange 2010 or 2013 integrated Archive functionality. Some others are using Enterprise Vault or ACA and some are using our ngArchive. There are much Solutions more, but all have their Advantages and Disadvantages.
As far as i actually know, ngArchive is the only solution what doesnt Need a Migration and still is able to use the Content stored in EAS (without require the EAS Environment - only the Documentstores will be used).
Martin