1 – The Apache Solr server has been upgraded to release 4.3.0 (if you looking at the specifics, please look at the release notes on http://lucene.apache.org/solr/4_3_0/changes/Changes.html)
2 – The programming model has been restructured and simplified. The search runtime can be accessed directly through a REST interface from the storefront. http://pic.dhe.ibm.com/infocenter/wchelp/v7r0m0/topic/com.ibm.commerce.developer.doc/concepts/csdsearchinteractionov_fep7.htm
3 – High performance as the processing is directly shifted to the search servers, making the code path efficient and faster. The search layer will scale more independently.