A friend of mine has a Sir9, after four years of ownership he cracked the cowling on the drive side drop out. He emailed Niner direct and after showing them photographs of the crack they replaced the frame FoC. Brilliant customer service.
He loves it, I’ve only ridden it a couple of times but when I did, I was more focused on the whole 29er thing rather than the feel of the frame so I can’t comment on the ride. He has the silver one now which is nice but the Hot Tamale was a better colour, I don’t think they do it any more though.
He has had issues with the EBB, not exactly sure what though.
I have experienced Pace customer services, around 16 years ago (brilliant) and around 5 years ago (rubbish)