I have found that since they reformatted their forum I go there less. I generally browse the "Ask RCCA" section and the announcements, and that's about it. As far as being a member of RCCA, however, it really depends on you desire to own the diecast first hand or second hand, and also how much you intend to buy,
Keep in mind you don't get a discount immediately (other than the fact that members pay $10 less than non-members) but as you go up in levels you do get a quarterly discount you can apply at the gold (spend $500 a year) or platinum (spend $1000 in a year) levels. You also get the comfort in knowing that if you get a damaged or defective diecast, you can return it to the source for an exchange or refund. Generally, it's less of a guarantee with an Ebay seller.
As "Brad K" said, sometimes the cars sell out, and they will cost more on the secondary market. Once you join, you get the monthly catalog as long as you stay active (on purchase a year) and you can decide what to buy directly from the company and what not to. I've been a member since 2002. At $20, that's $2 a year!