I visited this tentative WHS in October 2014 on my way back from my road trip to Bremen, Hamburg, Lübeck and Wismar. The Schwerin Castle ensemble is only 40 minutes away by car from Wismar and around 50 minutes away from Schalsee, a UNESCO biosphere reserve.
The Schwerin Castle ensemble is definitely on par with other inscribed properties on the WH list such as Muskauer Park in Germany/Poland or Lednice Palace in Czechia and although it doesn't add anything particularly new to the list, on a sunny day it is a very enjoyable visit (when in the area). Its construction was also inspired by the Renaissance châteaux of the Loire Valley such as Chambord.
The Schwerin Castle and its gardens are situated on an island in the city's main lake, Lake Schwerin, and after visiting the whole ensemble I'd recommend walking towards Lennestrasse and Franzosenweg for a fabulous waterside view from one of the 3 cafeterias (Ruderhaus, Ambiente am See or Schlossbucht).