I got mine from ebay- people buy bikes with them on and sell them unused. I use the DH version sometimes for the slightly stickier rubber but by and large I use the SX.
Never had any problems with the sidewalls, maybe because I weigh nowt, I'm not hard on tyres generally... having said that I've hit them hard enough to pretty much destroy a rim without flatting, another time I did flat the rear at fort william but also flatted the Flow Ex it was on They're not officially tubeless ready but do act like it. Hmm, can't think offhand of any other time i've managed to flat 'em, or the Clutches I had before (*), there's a fair number of cuts on one of them but nothing troublesome.
Basically they're just what you think- a halfway between single and dualply. I suppose only you know if that'll work for you.
(* Clutch not so good)