You can usually use lsof to see what the current file offset is in order to estimate copy duration.
Bah, right, forgot about that.
As for Mark's script, wouldn't have worked for me, as I ran the clone while booted off an OS X DVD. So BSD instead of Linux, no strace on the DVD boot, and no /proc to poke.
I did like how simple cp was to use though for cloning. No worrying about block size tweaks for speed, it just worked. And from what I could tell from initially trying dd, cp ended up finishing a little sooner.