I sold My 29" wheel mountain bike, But not for the reason you think.
I sold my Specialized Carbon Stumpjumper hardtail 29er about 7 months ago. Like most of us we get attached to our machines because we are emotional creatures. At a certain point, It's not just a bike anymore. For me it was a way to escape from my day, blow off steam or just get crazy. Everyone has something they do not want to deal with or just need a break from, It's ok, Im one of them. The 29er is just a another bike. Like any other bike, different styles can offer a different feel when riding, like when our mood changes. That's why I like to ride bikes.
I not only got rid of my Specialized carbon hardtail 29er, also known as a cross country bike, I sold everything I owned. I had a carbon Tarmac road bike and aluminum Crux cyclocross. Things were getting a little stale for me and I needed a change. The 9er was good to me. I will always have a special place in my heart for a hardtail mountain bike. Weather it will be another 29er, time will tell.
In my opinion the 29" covers a lot of ground quickly so that makes it efficient next to a 26". The bigger wheel is also a little slower. Where I felt it was in the steering and the acceleration. The first place I felt the sluggishness was on tight technical switch back climbs. I think any speed under 10 mph you really felt that big wheel taking it's time around a tight hairpin turn, like a big boat Making a turn. I have my eyes on a hardtail 27.5". I got to test ride a Santa Cruz Highball and it knocked my socks off. It was quick handling and steering was like a razor. It was an absolute weapon that could be used for good.
I can see why the 29er would be great for racing but the 27.5 was just plain fun. I can also see why most guys are looking at the 27 for trail or enduro riding. The 29er allows you to plow threw and over everything, that's what makes it fun. It will also work for people who may not have all the necessary skills to do so with out lots of travel and giant tires. In my opinion start out on a smaller wheeled bike and probably a hardtail if you really want to get the true skills of a technical rider. Save the full suspension big wheeled sled for unadulterated fun.