I've been a member for a couple of years now and I think it's a good deal. The first year there was no local chapter for me, which definitely limited the activities I could participate in, but the new chapter is small and growing.
Nationally, the club did five subsidized cost track days last year and are doing more this year. They have quarterly events with a meal, and usually some sort of monthly meet up (C&C, etc). Their forum does give you a chance to reach directly out to Cadillac engineering folks, although sometimes I've had to badger to get a response.
@MatthewAMEL already mentioned the tech talks - I thought the Brembo one was very good.
As I recall, you also get a discount on Cadillac merch (and I've gotten a ton of free T-shirts from the club), as well as discounts from their sponsors. A new car purchase discount would be great, but I can't say $500 off a $100K car is going to change my life.
We just had our chapter holiday get together yesterday and everyone that attended was entered for a raffle which included a free trip to Spring Mountain. Note, this raffle was at the national level. Yesterday I won one of the local raffled for a $50 gift certificate, so I guess that's half my yearly dues.
I'm not much for the car show scene, but I've gotten far more out of this membership than I did out of the couple of Corvette clubs (or Audi) I joined. Only PCA has them beat as far as subsidizing the cost of track time, but they're a huge organization.
P.S. Texas seems to be far and away the biggest chapter, so I imagine the experience there is quite a bit different as far as number and size of events.