Yea, I would say it's worth it; 2-3 years is still a fair amount of time to enjoy a console.
As far as mouse and keyboard support, I wouldn't have bought mine if it had no mouse support at all. For navigating the interface and surfing the web, you can just plug one in and it's good to go. I plugged in an old (5-7 years) Microsoft USB laser mouse, and it worked right off the bat. I downloaded a demo of The Darkness, but was unable to use my Microsoft mouse with that. That's not a problem though, because there is a device out called the "FragFX", and it apparently can be used with ANY FPS game on the PS3. Evey place that I've seen it reviewed at, says it works as advertised, so I'll be picking that up in the next month or so.