The primary thing you should understand about
DVC perks is that they are subject to immediate and unannounced change. Therefore, you should not even consider any DVC perk in making your purchase decision.
That said, there are a number of perks to being a DVC member. Probably the two biggest for most members are the AP discount (I think it's $100 off the AP price) and the ability to get
DDP on points stays at DVC resorts without having to buy park passes. We do not currently get any other discounts on park tickets. There are Members Only events, including Members Only cruises on
DCL.
There are a number of discounts -- 10% off dining at a number of restaurants (sometimes more at a few), spa discounts, free valet parking at DVC resorts, the discounted golf membership, occasional discounts at Cirque du Soliel, a 25% discount on cash rooms at DVC resorts (subject to availability, of course), and others.
We also have our own Member Services department, and I consider them to be an invaluable resource, plus the continually-improving Member website.
In addition to the DVC perks, we also get all of the regular perks of staying onsite that everyone else gets -- DME, free theme park parking, EMH, etc, etc.