Yes, On One's 29er Scandal rides very well, see my mini review linked below. I also have a really nice steel Kona Unit SS 29er that has pretty similar geometry and sliding dropout why have been bullet proof in terms of slippage and allows me to run 2 cogs at the back.
Orange71 and I changed cogs out on the trail in under 5 minutes at the first attempt and it's even quicker now I have the sequence worked out.
Here's the Scandal/Inbred geometry:
http://www.on-one.co.uk/i/q/FROO29SCVD/ ... pout-frame
And here is the Unit geometry:
The 2011 Unit has a slacker head angle and longer fork but I have never ridden one so can't comment.
Attached is a photo of the \Units sliding dropouts:
Another place to look is Niner's website. There SIR frame is highly regarded as is the Lynksey titanium frame.
I love 29ers