Although I am on the 29er side of the fence, and have not run a 26er for several years now... not all 29ers are equal. Some of the early ones were slow to steer, but many (especially Niner) have the geo dialled and you really lose no steering response on a good 29er.
You can ruin any bike with the wrong stem length, bars, and fork height. Its pointless having a 29er Vs 26er debate unless you get two bike side by side and test them both.
If all 29ers are rubbish then WMB would not put the SIR9 in the ten best bikes of 2009 (especially considering its a 3 year old hardtail, not some clever new fancy pivot'd thingy).
I race, I ride mountains, I ride bristol singletrack, I ride cliffs, quarries, Afan etc etc... and could not wish for another bike, my SIR9 is simply damned fine. And my shorter mate "crashy" is equally happy with his 853 Dekerf 26er.