It's odd... the funny thing is that I got into MTB about a year ago and started out on a 29er (not knowing any better), it's just what was at the LBS! No biggie, I rode it and it was confidence inspiring.... knowing nothing at the time, the video's I saw and what/how I saw myself (style I wanted/preferred) was more agressive xc/AM riding... but, the funny thing was I never saw many video's with big wheel bikes but it's what I started on so I rode it as aggressive as I thought/felt I could given my noob abilities. I first got bit by the bug about 4-5 months after getting into MTB while riding Monbo at LKNSP when I decided to just forgo the brakes... from that point I was hooked and it was clear to me how I wanted to ride.
I rode my 29er for almost 7-8 months before getting my 26 full squish. In that time though, the 29er felt nimble and I felt I could do what I wanted to do with it (note: was and am still a MTB noob) but to that point I felt comfy with how the bike maneuvered and it never gave me that sluggish feel cause that's what I knew/started with and got comfy with. Fast forward to now after about 8 months on my 26er and yes, going back to the 29er and I now understand what the 26 guys alway say regarding big wheels.
The point of all this though was that at a point and time I didn't feel like the 29er handled any differently than the 26er. Granted, I can probably attribute that to 2 things, 1) being a noob rider, and 2) That's just what I was used to. In the end, I feel like the wheel size only mattered based on what I had gotten accustomed to.
Maybe it's just me, but I say this only because I see it evident on youtube/the interweb where the world showcases crazy insane skills of riders all different shapes and sizes and even kids on all different bike sizes doing some sick type of riding. Most evident to me is when I see a young kid who probably had been on and should be on a 20-24 inch bike shredding on 26 wheels etc. If we scale that up, I would imagine that is the equivalent of an adult riding a 29er. Not to mention, I see riders that can kill it regardless what size bike they are on... In the end, we all win, bike tech continues to progress and we now have 3 tire sizes to choose from which I think is awesome. As with the majority of those surveyed, I've been bi 26/29er... and am 27.5 curious!