My two pence, I have a Soul, 3×9 drivetrain and On One carbon rigid forks. I love it – fast, nimble etc.
Just built up an Inbred 29er SS to make my own mind up about it all. SS, Salsa Cromoto forks and mid range kit. Weight is the same as the soul (no gears) and I have to say I love it more than the Soul. NEVER would have expected that in a month of fundays. I really can’t find a downside – apart from the tyres exploding obviously.