29ers have been around long enough. I've been on mine for about 8 years. Probably 10 plus on 26" bike before that. Since going 29 I've not owned a 26 so, I'd say that counts as die hard.
With that said I always felt drivetrains were not 29er friendly. Rear triangles and rear wheels on 29ers have always felt a bit flimsy to me, and just a bit too heavy and long to flip the back end around how I'd like. So, while I was a die hard, I also recognized their limitations. Still, the 29" wheel rolls so much better than a 26 with overall less strain on the rider I couldn't go back. (By roll I mean both "roll over", as in roll over chunk, and lower rolling resistance.)
The 275, on paper, seems like a good compromise with the issues I mentioned about - stiffer, lighter, more drive train friendly than a big hoop, but still retain some of the "roll over" and lower RR, and stability of a 29er.
My Stumpy 29er, my trail/AM bike, seemed like a good bike to experiment with. I was having issues with trying to run a fatter tire out back. It has short stays and with the inherently flimsier big hoop out back I was getting rub. Also, when pushed hard, I felt too much rear wheel flex. A big limiter on AM 29er setups is wheel weight. For AM you need a burly tire and rim, regardless of hoop size. Running big rubber on a thick rim gets heavy on a 29er - no way around it. So, I wanted to try a 275 out back on the Stumpy.
A rear 275 with a Flow Ex was built up on a King rear for the test. Mounting a Nevegal 2.35 made the most sense at the time. Yes, an expensive experiment I know. But, I knew if it did not work out with the Stumpy I could run it on my KM. As a side note, I was having similar clearance issues on the KM and knew I could make use of the 275 on that bike.
With the rear 275 mounted on the Stumpy 29er, and keeping the 29er up font, the bike feels great. Much better than a dedicated 29er for what I'm using it for. In many facets of handling, performance, and feel, this set up is superior for trail/AM riding. If anyone is interested reply and I could go into all that.
A dedicated longer travel 275 is too be my next bike for trail/AM. The Stumpy will return to full 29er mode but get faster, lighter wheels and it will be more of a xc bike. I'm convinced that is where mountain biking is going. AM 275. XC 29er. The in between all purpose "trail-bike" category could go either way.