Ok ok ok, there are some serious fallacies being thrown around here that really need to be straightened out. Personally, I think we need a sticky that goes through exactly what goes into outerwear technology. But for now I will try to clear up some misunderstandings. (Well fought Kevin)
Common misconceptions regarding outerwear technology
1)
"I live in - fill in the blank - therefore the only way for me to stay dry is to get a 20k/20k/Gore Tex/eVent/... jacket"
This is absolutely not true. Lets start with these WPB ratings that manufacturers use - I'm talking about ratings like 20K/20K. Sure I could write a few paragraphs on the waterproofing and breathability units and how that translates into performance, and that would all be perfectly valid.
But that is just about 100% irrelevant to the consumer. Why?
Because this how fabric gets made. A huge fabric mill in China (usually) has a catalog of fabrics that they have milled. A manufacturer says - I want XYZ fabric with in 20K/20K. The mill will make your order, the face fabric will be exactly correct but how does a manufacturer tell if the membrane is actually performing to the 20K/20K metric? They can't.
THERE IS NO STANDARD FOR MEASURING WATERPROOFING OR BREATHABILITY OF OUTERWEAR LAMINATES. This is why Gore never publishes any quantitative metrics on their outerwear, because they could be compared to a "30K/30K" fabric that sucks.
This means that the mill measures their laminates with their favorite technique, ie the one that yields the best results, and uses those numbers. That means that you have to find a reliable mill. Unfortunately, even if you found a so-called "reliable mill" you would have very little ability to validate that. (To put this in perspective, I measured some breathability numbers in our test lab last spring. With one technique I could consistently get breathability of 100K+ and with another technique I couldn't pick up a measurable amount of water vapor)
The only way you will get consistent performance from a membrane is by using a brand name mill. Why? Because they have a reputation riding on their fabrics.
HOWEVER, a brand name mill can put out shitty fabric and no-name mills can make really very, very good fabric. For instance, we source our black 3L from Schoeller in Switzerland, they have an awesome manufacturing process and one of the best PU lamintes laminates around. (Unfortunately, I cannot tell you the source of the Alpine Eagle fabric, it would be less lawful than I'd like)
Basically: Ratings mean absolutely nothing at all, nothing, period.
2)
Companies choose Gore Tex because it is the best
This is absolutely not true. Companies choose Gore Tex for two main reasons. 1) It sells well, people trust the name. 2) They don't have a choice - I will elaborate. You see, Gore Tex has been around for a long time, pretty much every major outerwear manufacturer has a Gore Tex license. But a few years ago, eVent came along. Some companies started to use eVent fabrics to see how they would sell. The consequence?
Gore Tex immediately revoked their license. Gore knew that a company could not make a full lineup using just eVent - a new less established name. They set an example with a few companies and everyone else politely turned down eVent for fear of losing their licenses. Monopoly scare tactics (check out this great article that puts it in rather polite terms:
http://www.outsideonline.com/outdoor-gear/Insane-in-the-Membrane.html).
So that's all I really have energy to type. Obviously I'm not being too biased toward our products. In this case I think its more important that consumers actually know what goes on in the industry because outerwear is such a BS market technology wise. There is just no good way to quantify the technology.
If anyone has specific outerwear questions, I will happily answer them in this thread. I actually know quite a lot about this topic.
Last but not least, read this article, every single one of you: (thank you Kevin)
http://blistergearreview.com/articles/outerwear-101 
