I have it and its mostly useless except that it gets you discount at few top tier conferences. If you go to lot of their conferences, the membership will almost pay for itself. The free stuff that comes with membership is virtually useless and many times borderline spam.

I'm however considering cancelling this as my protest against their mostly pay walled publications. Interestingly even if you have membership they still don't give you access to it! In many ways they are as bad as Elsevier but have managed avoid attention because technically they are "nonprofit" on paper and they run lot of top tier conferences.