Pricepoints ...
From the enthusiast standpoint, we all love our 29ers and we won't go back. Want some reference go over to mtbr.com and check out the 29er forum. It is the most popular forum there.
From the manufacturers standpoint, I think they are merely interested in sales. When the "race hardtail" disappeared I think it made a whole in the spectrum of pricepoints in a companies lineup. The 29er has some unique attributes and it fits that "high end hardtail" entry quite well. You'll notice that very few companies ship 29ers with junk parts. The point of the excercise is to create a bike that sells for more money.
In the end only the consumer can tell if it's worth it. However, I believe that if 29ers were meritless they would have disappeared well before this point. It is not too early to say that 29ers are here to say. They have branched from being a singlespeed oriented offering to full blown medium travel trail bikes offered by pretty much EVERY large bike company. Perhaps 29ers will never completely dominate the XC market as I suspect. However, calling 29ers a fad is absoluetly ridiculous.