Specifically, the main new functionality is the new dex (under Exchange) and the offline armory signing feature (under Create New Address...a tutorial for this will be forthcoming before release).
Please note that your preferences may not all show up correctly on this server, as it's running an older version of user preferences, as it's just for test. If you use an existing wallet, just ignore it if your addresses are named the old names, or not all of your addresses show by default (you can just click on Create New Address to add the rest of them). Changes to either address names or # of addresses created here will not affect your changes on the production counterwallet.co
EDIT: Also, please avoid being logged into the same wallet account on both this server and the production server, if you are making dex orders of any kind. This is to avoid any automatic BTCPays from happening multiple times.
Excellent work ! A small suggestion, since you the protocol doesn't allow lowercase assets, maybe the field in the DEX should uppercase every input ?