About 10 years ago I jumped from 26rs to 29rs when the geometries had you riding like unicycles high up. Though when 27.5rs came out they didn't feel much different from the 26rs so they never caught on for me. Eventually with longer TTs, shorter stays and slacker HT angles, 29rs are feeling just right. The ideal tire size for me are 29x2.4 at the moment. But I'm also gravitating towards 27.5x2.8 for full suspension. Size is close to the 29rs but more contact to the trails to offset my lack of skills.
Then there's the 29+ which is in it's own world. What a fun size, yes turns like wagon wheels but so much rubber. The ultimate bike packing tire size IMO. Long live the 29rs