Fred,
I really wouldn't call them perks, but there are a few things for
DVC members. These are on the 7 day cruises, not the 4 day.
There is a desk up on deck 4 and if you stop by and chat they will usually have some little freebie to give you (we got a pin in 2001).
There is a member party held late one afternoon with free soda or wine (maybe mixed drinks too I don't drink so I don't remember). You get a baseball cap when you walk in and there are chips, pretzels, nuts on the tables. They played a game and gave away some DVC prizes (note cubes, luggage tags, bags).
There is also an info session that is open to both members and non members. I went to this and got a DVC can cozy.
Like I said these were all on the 7 day. When we took the 4 day in 2002 they didn't have any of this.
Of course when we went on the SS Member Cruise in Feb. 2003 there were lots of perks, but that's because it was a special DVC cruise.