My late '06 is still running, albeit not as good as it once did.
The combo drive died (or at least, when it's connected, the computer won't boot.), the Airport card is failing/failed, it only stays connected if it's within a couple feet of the router, if it's far away, it stays connected, then over a short amount of time, the signal starts dropping until it can't even pick up a connection anymore.
But other than that, it's been a real trooper. Still using it as my HTPC, hooked up to my 46" Sony Bravia rear projection TV. I'm really impressed by it, but also disappointed that things are failing. Been considering replacing them, but with my luck, the root issue of these things dying is probably something bigger, although the computer performs just fine.