|XP is just a number|
I think that all 'new' methodologies only work for those who haven't already established their own methodology.
If you impose an always drive on the left (or right) rule, where there was previously no such rule, you'll see a considerable improvement in traffic flow. But take away an experienced carpenter's Yankee screwdriver, and force him to use an electric one and his productivity will fall sharply.
The problem with new methodologies is that they become self-serving. Someone strings together half a dozen simple--and often common sense--ideas that work for them and their group and utilise it successfully on one or two projects. Inevitably, someone (usually someone else) sees the possibility to make money from them.
So they take those half-dozen ideas and formalise them. In the process they throw in a few buzz words de jour, some self-evident good practices wrapped over in marketing speak, and generally baulk up the whole thing with a few tortured analogies. They then set about the task of selling you (or more likely, your boss), on their "solution", with nary a care for whether it actually solves your problems.
A couple of questions to ask yourself (or your boss) when considering any new methodology:
Snake-oil salesmen have been around for hundreds, if not thousands, of years. The products and pitches may change, but the underlying scam hasn't. It still relies upon taking something of low real cost (and usually little real value), and pitching it as the Golden Hammer, Silver bullet or Zauberkugel for a wide-spread, intractable and costly problem.
And there is still one born every minute!
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.