It's as real as any of them. A good number of people have found it works better than what they were doing before. Some times (but not always) they can teach it and make similar improvements happen for other people. That's about the best we can say about any of these things.
Is it the best possible thing? When it works, does it work for the reasons we think it does? Are we turning exactly the right knobs to adjust it? Will there be something better? Time will tell.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi
There are a *lot* of companies out there that report a drastic improvement of productivity and quality after adopting an Agile approach.
I'd assume that when RUP was new, it was a drastic improvement, too. I'm curious to see what's coming after Agile, but for now I don't see anything on the horizon. (Contemplative Programming sounded interesting, but it seems it disappeared...)
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus