Copper's proper. That's the saying, anyway. But the problem now with copper for your plumbing has nothing to do with reliability. It's cost. Over the past year, the retail price of copper tube for plumbing has almost doubled. However, there is a great money-saving alternative.
Using PEX for your new water lines can save you a lot of money. It's a polyethylene crosslinked tube designed specifically for water. PEX comes either semi-flexible or rigid, and the joining technologies it uses are every bit as reliable as soldered copper joints. The Plastic Pipe and Fittings Association has some great information on PEX.
The cost savings of using PEX over copper are huge when you do the math. For example, right now ten-foot sticks of half-inch copper run about $13. You can pick up a 100-foot roll of half-inch PEX for under $60. Right away you'll save about half the cost of materials.
The labor saved with PEX is outstanding. I've worked with both copper and PEX for water lines, and PEX is much easier and faster to install. Overall, the time it takes to pipe water through a house in PEX is less than half what it takes to run copper.
If you decide to go all the way with the cost savings and run the water lines yourself, it's a lot easier than it would be with copper. There is no soldering to learn, and the very rare leaks are much easier to fix. The fitting tools for all the different PEX systems are easy to use, and some places will rent them for the day.
If you're going to hire a plumber to install PEX water lines you can still save a lot of money, but you can't always assume this is how it will go. The best way to get a fair deal is to ask for three separate bids from each plumber you meet with. Get a bid on the waste lines, a bid on water lines in copper, and a bid on water lines in PEX. That way, you know exactly what where your money's going.
Don't miss Alex's recent post on graphic wall decals. If my wife would let me do something like this, I would!