Personally, it took awhile for Bo9S to grow on me, but then boy, did it ever.
I like the flavour of this discipline a lot more than most of the flavour of the book itself. Seems to lend itself very very well to a Swordsage, sage/rogue, or swordsage variant with sneak attack. You've made a lot of nice maneuvers for combos that rely on the sneaky skills and/or sneak attack in place of regular weapon damage. Covers the BAB weakness of both the rogue and swordsage very well. Treats the rogue (hmmm, or arguably the right monk) even nicer than the Shadow Hand discipline. Really well-designed, both mechanically and flavorily.
One note, though - I would consider editing or cutting the Expert Slash part of your tactical feat. It's got two nice, balanced combat options, and then Expert Slash just undoes most of the penalty of using Oncoming Storm Expertise in the first place. Sure, it's a feat with a lot of prereqs, but it's a combat option that almost always assures it's own use (Raise your to-hit. If it hits, do more damage) and makes one of it's prereqs unbalanced.