After 2 yrs of finding 29ers I jumped on my mates 26" Yeti 575 the other day. The bike is near as makes no different the same as my Covert 29 in terms of size and geo apart from the wheel size - both 140mm travel, both similar if not same geometry, both bikes set up the same as we're the same height. I took it down a familiar really rocky technical descent, so sections where you have to slow a bit to pick your way round big boulders, some medium sized boulders you can grit your teeth and ride over, and some faster flowing berms sections.
It did feel weird jumping on the 26er and though the bike rode fine, the ride was much rougher. On my 29 er I feel I could go faster over the course if my balls were a bit bigger, on the 26er I feel I couldn't have hustled the bike much quicker at all even if I had the skills. In just felt more unsettled, more knarly and more on the edge. Great fun though, I also didn't really feel any benefit to the smaller wheels in the slower technical sections that demanded more maneuverability, the 29er is just as maneuverable.
Go, on, far from an objective and definitive test, more of a seat of the pants feel, but I 'm happy with my 29ers. Not dissing 26ers, my mates Yeti s a great bike. I struggle to see what the fuss is about. Are you really going to change your perfectly good 26er for another bike purely and solely for wheel size?
You get this in alot of sports. New kit comes along, people initially reject it, but over time people adapt, the kit evolves and before you know it the sport has progressed as people start doing things that were previously thought of as impossible. There is an element of adaptation that is needed and an adjustment of technique. There is nowhere for 26 inch wheeled bikes to go. They've reached the end of their development. The sport needs a change to enable further development. But for the recreational rider, it doesn't really matter. Ride what you've got and enjoy it.