Yep...
http://clockwatching.net/~fin/stats/
We use it at work in a few backup machines and I'm pushing for it to get used more. But its more then stable, mdadmin and the newer raidtools are awesome, you can daemonize event checking, its solid, probably preferable to hardware raid even compared to monster good cards like the LSI Megaraid or the 3ware 9k series.
Cheers,
Finegan