The two that are currently being offered that save me the most are the free internet for points stays and the $100 AP discount.
If these go away, I won't mind the loss of internet (as I don't have to get on the computer while I am away), but the AP discount would be sad.
But, as already mentioned, don't ever buy for perks. When I bought in 2009, we still got free valet. We went on our first DVC stay in August and I used it at VWL and LOVED it!! I was so excited about this perk.
While, not two months later, that perk disappeared. Not that I bought for that (didn't even know about it when I bought), but a bit of a let down when it was gone.