I had a Horsethief until v.recently - unfortunately I only got to use it for 2 proper rides before it was pinched! (I'd only had the bike for 9 days). I really liked the bike and am very F'in annoyed that it got nicked - so I make no apologies for the following glowing mini-review.
I'd demo'd quite a few 29er full-sussers before getting the 'Pony', and I/my OH also had a Spesh Camber 29er (also nicked), so I've some experience of FS 29ers.
I read the review that mentions that that the Horsethief can be a 'bobber' on climbs, so before I borrowed the demo bike, I contacted Salsa for advice on suspension set-up. The guy at Salsa recommended starting with as little as 10 to 15% sag, then experimenting by increasing sag a little bit at a time to suit the terrain & my riding style. I like the challenge of rocky technical climbs, so I settled on 20% sag - with this amount of sag, I felt that it was a better than average climber off-road (on tarmac it could feel a little bit 'ploddy' even with tyre pressures bumped up and Propedal on). I did a few small jumps on the second ride and with 20% sag, was almost getting full travel from shock - so it seemed a good balance between climb/descend.
I ran the bike with the Fox 34 in 120mm travel, and it absolutely blitzed one of my favourite descents - it felt like a complete monster truck on descents - God only knows what it'd be like with the fork at 140. I had planned to try the fork at 140, but personally I think it might make the steering a bit wandery on climbs, and raise the bottom bracket too high for my taste.
Sizing wise, I'd agree with the previous comments. I'm 6' with long legs and went for a Medium, as I prefer a bit of manouverability over super-stability. Even with the med frame, a 70mm stem/720 bars didn't feel cramped, and I was looking to try a 60mm stem on it.
FWIW, if you go for a frame only, I think you'll find that even the 2012 ones now come with a Kashima CTD shock (rather than the std RP2 that my full build bike came with). I reckon the CTD would be the perfect shock for the bike, particularly in trail adjust version.
TBH, the only other bike that I would consider replacing my Horsethief with would be another one, or if I win the lottery, a carbon Tallboy LTc. (Personally, I preferred the Horsethief to the alloy Tallboy LTc, which felt like a bit of an anvil).
P.S. Blatant bump of my stolen bike thread [url] http://singletrackworld.com/forum/topic/stolen-specialized-camber-29er-and-salsa-horsethief [/url]