At this time there are 2 and only 2 lawsuits involving PEX. In fact they do not involve the tubing itself but in both cases involve "Chinese" brass fittings used with the PEX.
The Kitec Lawsuit is based on an improper grade of brass used in the fitting and possible dissimilar metals that result in "Dezincification" of the brass fitting. This process is accelerated under aggressive water conditions. Where interestingly enough copper would be a bad material choice.
http://www.corrosionsource.com/technicallibrary/corrdoctors/Modules/Forms/dezinc.htm
The Zurn Lawsuit is also involves the brass fittings as being incorrectly designed and manufactured. The fittings IMHO (I am not a machining and metals expert) are defective as a result of being too thin after machining with too small a radius built into the machined ridges of the barb resulting in a weakness.
Pex tubing is a great material that is made by many manufacturers. It is resistant to corrosion & chemicals, scale buildup, freeze damage, water hammer & other noises, & erosion from high velocity. It is very inert so water purity is not an issue & it retains heat in hot water applications. It is inexpensive compared to copper both in material cost and labor to install. The material lends itself to repiping very well as it is tubing that can be threaded through smaller/fewer openings in walls and ceilings than rigid pipes. The material has a proven track record extending back to its development in the late 1960's with years of usage and billions of feet installed.
You are judging an entire product catagory by the results of an "Cheap" brand sold in big box stores! This is the equivelent in saying all gas tank type water heaters are junk based on the experience of installing a Whirlpool Flamegard/Flamelok water heater sold by Lowes or, saying all large dia, flush valve toilets are junk based on an experience of installing an Am. Std. Champion toilet also a top seller at big box. When plastic tubing came out in the late 70's- 80's there were 2 choices PEX and Polybutylene. We picked the wrong one and went with Polybutylene while in Europe they went with PEX. Now stung by our experience with Polybutylene we are resisting the idea of using PEX, based on our experience with Polybutylene. Add to this the 2 defects of "Cheap Stuff" we have plenty of ammo for those who are resistant to the idea of using PEX. Does this completely negate the successful history of PEX use here and in Europe? Should we base our opinion of every other PEX manufacturer based on what has happened with Kitec & Zurn?
I say if you do you will find your self hanging out with the dinosaurs! When you go and bid jobs in Copper and CPVC against PEX you will find yourself losing the bid! The material and labor costs will kill your bid its that simple.