The Greens are celebrating because the Speaker has granted their request for a "conscience vote" on the enabling legislation for John Key's corrupt Sky City gambling deal. They shouldn't be. Why? Because he hasn't given them what they think he has. They requested, and were granted, a "personal vote on [a] conscience issue" under Standing Order 139. But a personal vote is just a procedure, in which MPs vote old-style through the lobbies rather than having the votes called out by the party whips. Most "conscience votes" are taken in this manner, but in and of itself, a personal vote gives no particular freedom to MPs in casting their votes - that's, as always, between them and their parties. And the National Party is perfectly free to tell its MPs to go to the appropriate lobby and vote the party line, on pain of suspension from caucus or other consequences, just as they implicitly do for the more usual party votes.
And the Greens know this. They've been effectively party-voting in personal votes for years, being one of the few parties which is brave enough to have policy (and therefore be able to be held collectively accountable by the public) on traditional "conscience issues", such as marriage equality and child-beating.
The tactic is obvious: a personal vote gives them a greater chance of peeling off the one or two conservative, anti-gambling (or alternatively, pro Auckland) MPs needed for the bill to fail. But their framing of it to the public is either stunningly naive, or downright deceitful. And with Key's reputation as a wheeler-dealer on the line, I don't think it will work (in which case they'll what? Accuse National of party voting in a conscience vote? That would be hugely hypocritical).
(Meanwhile, its worth noting: the idea of a "conscience vote" appears nowhere in our constitution, and nor should it. The freedom parties grant to their MPs is up to them. If we think a party is too restrictive or too lax in that balance then we can vote accordingly).