I personally got it just so that no one else in my company would ever need to do so; there are stupid companies which won't buy a product without integration, and where they have artificial requirements for integrators being certified. Given that it is only 1% of useless pain to enable 99% useful rewarding stuff, I found the sacrifice worthwhile.
But to be clear: I believe pretty firmly that for technical / software security, the CISSP is useless.
I'm not sure how I feel about SANS/GIAC. Absurdly expensive IMO, but potentially actually has some value for sysadmins doing system security. I can't think of what CISSP is actually good for, except maybe trivial pursuit - crappy consultant edition.
I'm under no illusions about the certification's marketplace value and I doubt I would have ever paid for the course/cert on my own, but it felt like one of the better formal trainings I've been through in my professional career (which, granted, isn't saying a whole lot by itself).
Also, the certificate comes mounted on a comically oversized plaque, which provides some entertainment value.
Maybe the perfect cert would be a useful tool for some purposes (corporate hiring, huge projects with consultants doing low-level IT, etc.), but those are crappy jobs (and not really "expert" in any way).
More importantly, the extant certifications are all crap. CISSP in particular. Get it if an employer requires it, but it's independent of your actual knowledge and learning process.