Yep. Exactly the same here, I have SS and SBSS Series 3. Works fine, even with data. You can turn on Auto Switch so you can just put on a Watch and it becomes the active one.
Apple has also recently improved using two Watches. For example, before new music would only sync to the most recently used Watch. So overnight only one would ever download new music. Now both will update at once assuming they're both on charge.