I think it depends on where you ride... Personally, I like having a full range of gears... I used all three front rings this past weekend... but at the same time, I run a 11-30 cassette... When I build my 29er, will I sing the same tune? Who knows... but considering it's quite likely the bike will also be 8 speed (just realized I have at least 2 complete XTR 12-32 drive-trains, in good condition, not being used...), it's possible.
Most of my XC friends all run 1x9 set-ups now... yet I remember how they looked askew at me when I showed up for a ride with my Chameleon with it's slalom set-up... basically: a 1x9 with an MRP chain guide... (my only 9 spd bike) about 10 years ago...
I guess the difference is, I hate walking...
HATE it... and I'd rather crawl up a climb in my granny gear than push my bike...