Community Requested Features
DSpace 1.6 includes the top three most desired new features based on a survey of the user community conducted last spring:

Improved Statistics Feature: The new version of DSpace includes better usage statistics, in particular for individual items and bitstream downloads, which has emerged as a primary requirement within the DSpace community. Thanks to contributions from @mire, who open sourced the back-end of their commercial statistics package for DSpace. 1.6 now contains a full fledged usage event logging and query service based on the Apache SOLR search platform. Rather than storing item views in a log file, or in a database table, they store the item view data in a SOLR index. This means that statistics are stored in a search engine index that can be queried very fast and efficiently and in powerful ways. The out-the-box simple statistical views are available for each item, collection, and community in both the JSPUI and the XMLUI. Information is given about item views, bitstream downloads, and user metadata, such as the location the users of the repository came from. Basic statistical reports are available that fulfill the community 1.6 requirements. The benefit of using the SOLR index is that it holds a lot of statistical information, so that in future the statistics feature can continue to be improved to include more information based on additional community feedback.
The new statistics feature comes with a script to convert your old dspace.log files into the new format, which means you can import statistics from old log files for as far back as you have archived logs. (Contributed by the @mire staff: Mark Diggory, Ben Bosman and Kevin Van de Velde, JSP interface contributed by Kim Shepherd from the Library Consortium of New Zealand)

Embargo: With 1.6 it is now possible to configure a DSpace instance to have an "embargo" feature for bitstreams that need to remain dark for a given period. The embargo feature has been written as a framework rather than a fixed implementation. This means that it is possible to write your own embargo rules in Java classes. Out-the-box 1.6 includes a simple implementation that should fulfill the needs of many users by allowing an embargo lift date to be set during the submission of the item. The metadata will be viewable, but the bitstreams are locked from public view until that date has passed. A script runs daily to lift any expired embargoes and make the bitstreams public. (Contributed by Richard Rodgers from MIT and Larry Stone from Harvard University)

Batch Metadata Editing: DSpace 1.6 now provides a batch metadata editing tool which can be used to change, add, find/replace metadata as well as facilitate mass moves, re-order values or add new items in bulk. The batch metadata editing tool was developed with the assumption that there plenty of existing tools for editing large amounts of metadata. Rather than trying to re-create this functionality in DSpace, the developers enabled the import and export of metadata into these existing tools. The batch editing tool produces a comma delimited file in CSV format which can then be used in Excel or a similar spreadsheet program to change metadata. Metadata can be exported for entire collections, communities, search results, browse results, or for the whole repository. Repository administrators can batch edit all metadata (e.g. perform an external spell check), batch add metadata (e.g. add an abstract to a set of items, add controlled vocabulary such as LCSH), batch find and replace of metadata values (e.g. correct misspelled surname across several records), perform mass item moves between collections, enable the batch addition of new items (without bitstreams) and re-order the values in a list (e.g. authors) via a CSV file. Once changes have been made to the CSV file, it is uploaded back into DSpace which detects the changes and displays them to the administrator. If the administrator confirms that the changes are correct, the changes will be made in the repository. (Contributed by Stuart Lewis from the University of Auckland and Kim Shepherd from the Library Consortium of New Zealand)

Highlights of Other New Features and Improvements
The original intention was to finalize DSpace 1.6 as soon as the community requested features above were completed. However, while the new feature work was on-going, the DSpace community worked its magic, and once again came up with loads of other new features and improvements to include. The list below highlights a handful of the additional new features and improvements:

Delegated administration: Previous versions of DSpace have allowed the system administrators to delegate permissions at a collection level, so that individual collections could be managed by a collection administrator. Some aspects of this feature have not worked as fully as expected, such as allowing collection administrators to edit or delete existing items. In DSpace 1.6 this administrative feature has been extended and made fully configurable so that permissions can also be delegated at a community level. (Contributed by Andrea Bollini from AePIC Team CILEA and Tim Donohue from University of Illinois/DuraSpace)

Authority control: A new authority control framework has been included which allows authority sources to be developed for metadata input. For example, you may wish to link up author names with a local or national identity database (via Library of Congress Name Authority), or link up publications to their ISSNs (via SHERPA RoMEO). In addition to the raw functionality, AJAX lookups are enabled to allow auto complete functionality to show users matches to the data as they are typing. (Contributed by Larry Stone from Harvard University and Andrea Bollini from AePIC Team CILEA)

OpenSearch: An open XML search results system. DSpace 1.6 now supports OpenSearch format, allowing repository users to add DSpace to their list of search engines in web browsers like Firefox, Internet Explorer and Google Chrome. OpenSearch also allows you to subscribe to a search via an RSS feed. (Contributed by Richard Rodgers from MIT)

OAI-PMH / OAI-ORE harvesting support: This isn't the ability for DSpace to expose its items via OAI-PMH, which has been available since version 1, but instead is a facility that allows DSpace to harvest other repositories and import their data into DSpace. It is now possible to create collections which harvest all their items (metadata only, or metadata and files) from another location via OAI-PMH. This could be useful if you want to mirror all or parts of another repository. (Contributed by Alexey Maslov from Texas from A&M University)

Batch imports and exports using zip files: Since version 1.5.1 administrators have been able to export all the items within a community or collection from the administrative user interface. In 1.6 administrators have the ability for the command line version of the batch importer and exporter to handle zip files of multiple items, rather than requiring an item directory hierarchy. This means you can export multiple items to just one zip file, transfer the single file to a new server, and re-import it.(Contributed by Stuart Lewis from the University of Auckland)

Command launcher: A new command launcher has been written to replace all of the old DSpace command line scripts. This means that one script can be used to perform all command line functions, and works on all platforms. In the past we only shipped DSpace with UNIX scripts.  The new launcher allows Windows users to use the same commands as UNIX users. (Contributed by Stuart Lewis from the University of Auckland)

For a complete list of the 1.6 modifications, please refer to the feature/issue tracking tool, JIRA, or the Release Notes.