Some local bldg. codes allow plastic (PVC I think but not sure). I've also heard that in some places they are using flexible tubing which can be 'pulled' through the wall like electrical cable. I suspect the tubing is something like the stuff typically seen under kitchen/bathroom sinks.

I would definitely reccommend copper.

I'm in the middle of a copper repipe myself.
If you're in the Los Angeles area, let me
know and I can tell you who the *WRONG*
plumber is. ;-)

-- J.S.

Do it yourself with copper. Some plastics have been unacceptable for potable water. Save it for the drains. It isn't that hard of a job.

Sweating copper is cool