If you are upgrading from a version prior to 2.5.1, make sure to go through all the release notes available here.
#5593: Fixes a bug where trap advanced matching rules were not working
#5600: Fixes a bug where it was impossible to add or modify a poller
#5533: Fixes a bug where it was impossible to update the severity level of a service
#5307: Tooltips messages were not translated in the Broker configuration form
#5664: Enhances loading time of the service detail page
#5439: Enhances loading time of the meta service page