Go ahead and download Solr 5.4. The major feature is a new Admin UI which lets you manage Collections, not only cores. The new UI also allows you to manipulate the schema through Schema Browser tab.
Also, the Analyzing suggesters can now filter suggestions by a context field, this was one of the issues Cominvent contributed to. Another was SOLR-8269 which removed the commons-collections security vulnerability. For a complete list of changes, please see Changes.html