I've been running 1x9 on my 5spot, built as a light-ish trail bike, for about a year.
At first I ran 34 front, with 11-32, which was fine for my local hills but not as versatile as I wanted for big days away.
It also felt like I was wasting traction from the suspension because the pedal torque was causing me to break traction with the ground on the more dusty or muddy stuff. No problems with top-speed pedaling though.
This is intended to be my go-anywhere, do-anything bike, and I felt it was a little too restricted, so I put a 32T chainring on the front which was a bit better traction/torque wise, but felt a little too slow at the other end of the block.
I've now settled with an 11-34T cassette and the 32T chainring. Its just the right side of the traction/torque issue for nearly any climb I care to go at, and I've accepted that until I switch to 10spd, the higher speeds will be slightly limited.
Just for peace of mind, I run the shortest chain I can get away with, an SS chainring and and XCX chain device.