The ANSI/ISO standard for C++ was ratified in 1995. It was in draft form since '91, and the so-called final draft was around for about two years (mostly awaiting Denmark's approval IIRC). It is now 2006. That's more than 10 years (as your Smalltalk numerics library will surely tell you), which makes it a "mature" technology by your own definition of the term.

HTH