Great start to the series - seems that they're going about fixing the main issues that the first series had. The weak, pointless side characters are either dead (Tommy) or getting much less screen time (Thea).
I love that the league of shadows is being properly introduced, and the mention of Ra's al Ghul was a nice surprise - DC has always been very protective of anything related to Batman. The execution in the clock tower was entirely unconvincing though (the league of shadows assassin didn't even try to fight back?).
Really not looking forward to superpowers appearing though... I can't help but feel that it will spoil the dark and gritty feel of the show.
As for the "why don't people recognise Oliver" question - well, he's always careful to show up at night, and keep his face hidden from the light. As mentioned before, he has already gone to lengths to eliminate himself from suspicion, by having Diggle pose as the arrow while he was in custody. I would like to see Laurel recognise him in this way eventually though... She's inevitably going to learn the truth at some point, and rather than it being a 'big reveal' made consciously on his part, I'd prefer to see the two of them end up in a situation where she gets too close to him and sees his face (maybe he throws her down to avoid a bullet / arrow / whatever and she makes the connection). We'll see...
edit - on the Island we saw Slade Wilson burning. Is this his transformation into Deathstroke? I assume that he will blame Oliver for his maiming, since he ran back recklessly for Shado.