Initially I didn't get the Drow Blademaster's "Flashing Blades" ability (or the Human Ranger from Cormyr, for that matter). Then I realized that, it could stab the same adjacent creature that it initially damaged, effectively allowing it deal 30 damage almost every time (I read it as a different adjacent creature.)
So now I'm looking at the Drow Assassin and trying to make a similar realization... How exactly is the "Hidden Blade" ability useful? It seems cool that it's 10 damage stab happens weather or not you deal damage (or even attack), but an "adjacent tapped creature" seems a little restrictive. The only strategy I can come up with is to rage attack a creature prior to movement, then position the Assassin so that he ends next to a tapped creature for the extra blow? Can any one read anything else into this?
Still, "Flashing Blades" seems better and would be used more often (i.e. every time it deals damage,) so I'm not sure the extra level is worth it for the Assassin.