pex, kitec, etc are extensively used in residential and commercial applications in the u.s.

http://www.jupiterheating.com/help/kitec-xpa-pipe.html

am also starting to see pvc water supply piping used more often due to copper prices

PEX is super easy compared to sweating pipe...

I had PEX pipe installed for a kitchen sink where the piping would not be accessible before pressure testing the system. I also had some installed for my hot water loop from a boiler to heat coil in an air handling unit.
It's simple to install, so less labor costs. It takes a completely different set of tools though, so make sure your saving money vs copper before you buy the tools.
If you do your homework, you should be able to install it yourself. Just know the difference between potable and non-potable piping. And talk with your building inspector before you begin the work.

PEX is becomming more common here in the US but I wouldn't recommend using it for just remodeling one bathroom. It works best in applications where it can be "home run" back to a manifold mounted where the water enters the building and then run continuously with no unions or joints right to the shut-off valve for the fixture you're serving. It's a great choice either for new construction or for replumbing an older house where you don't want to have to open lots of walls.

For just doing one bathroom (unless it's a huge bathroom), copper isn't really prohibitively expensive. To use PEX you'd need to buy or rent an expensive crimping/flaring tool (not the cheap ones they sell at HD/Lowes either) and it would be hard to justify the cost of the manifolds.

A better low-cost alternative might be CPVC. It's easy to work with, doesn't require special tools or connectors, and can be joined to copper easily. If you use CPVC just remember for all your threaded fittings to use the ones that convert the CPVC to a brass thread. The plastic threads are prone to cracking and are not code allowed in most areas.

I recently did a big plumbing project myself and found this forum and this forum to be very helpful in comparing pros and cons of PEX/copper/CPVC and getting installation tips.

If you do decide to go with CPVC there's also a little-known company called King Bros. Industries that makes fittings where you can solder one end to existing copper and glue CPVC right into it. Makes it very easy.

thanks bryan.

I agree. If its a rather small job switching materials is not worth it unless your determined. Also, If your going to DIY it consider if you this will be your only project you'll ever try. It might be worth hiring a pro. Anyway, copper piping has a proven track record. Having the skill of sweating copper pipe has saved me alot of money. I like pex and have had it installed it in renovations. It simplified the job. Installation is quick. I have not home run a project. It's a great way to do a plumbing job but not required. I even had a portion of a pex piping freeze solid for a couple days and it didn't burst...it seems to stay flexible way below freezing. CPVC is easy but I'm not big fan of it . In a way , don't look at the cost of the different materials. Look at it as if you would have to pay someone else to do the work. Even the most expensive materials with the required tools become reasonable. If you are a regular DIYer than the tools will always have value

I hear the crimping equipment is expensive. I know the young plumbers love the stuff, while the old timers hang onto copper.

Studio43 - the freezing aspect of PEX is one reason I'm considering it. Still I'm leaning towards doing copper. Have the skills with sweating copper so no need to hire a pro. The crimping tool for PEX is about $150 per tube size or $200 for an interchangable size crimper. My blow torch, flux and solder weren't that much. I'm not exclusively looking at cost since I'd like to learn a new system. Then again, I can't ignore cost either.