Experience with Third-Party memory (Cisco)?

With all the talk lately about the growth in routes, I got to thinking about upgrading the memory in a couple of my routers. Does anyone have experience using third-party "guaranteed compatible" memory. With Cisco's discount it looks like I can upgrade for $5k vs $700 with third party memory. I'm just wondering if others have used it, and how it's performed, or if it isn't worth the risk. thanks