This release comes with tons of changes and improvements.
https://bisq.io/downloads/

Most relevant changes are:

• Support for other base currencies (next to Bitcoin we support now Litecoin and Doge. Dash will come soon as well)
  
• Using a fee estimation service for setting the optimal transaction fees to avoid stuck transactions in times of high blockchain congestion
  
• Support for custom security deposit
  
• Multi language support. Currently: English (default), German, Spanish, Greek, Portuguese and Serbian
  
• Dynamic trading fees (depends on trade amount and distance to market price)
  
• Many technical improvements like more compact trade protocol, usage of Protobuffer, BIP 44 wallet,...
  

Please see the full release notes below.

As that release has very profound changes it is not backward compatible to the earlier versions. It uses a new network which is separated from the current trade network. So your offers from the current application will not be visible for users who are using the new version.
If you want to migrate to the new version you need to close your offers and withdraw your funds to the new application. You can run both applications in parallel as they are using a different data directory.

Please double check with cmd e in the old application if no funds are left over (some bugs might have caused that the balance displayed in the UI is not correct).

Please use small amounts when starting trading in the new application as with so many changes there are some risks for bugs (though it is thoroughly tested).

https://github.com/bitsquare/bitsquare/releases/tag/v0.5.0