I only saw the second half of this match. From what I heard, the first half displayed more of what we've seen in the last two matches; Arsenal failed to create any decent chances. For most of the second half, the match looked likely to end in a scoreless draw, especially after Santi Cazorla conspired to blast the ball up into the stands from 8 years out, when he was under virtually no pressure from the QPR defense. But the game changed soon after that, when QPR defender Stephane M'Bia intentionally kicked Thomas Vermaelen in the shin, after Vermaelen had shouldered him to the turf (earning a free kick for M'Bia). The referee had absolutely no choice but to show M'Bia a straight red card.
From that point on, the game improved pretty dramatically. The Gunners started getting shots on goal (finally), several of which were very well saved QPR goalie Julio Cesar. The Gunners's goal finally came after a nice cross into the box by substitute Andrei Arshavin (replacing the consistently wasteful Gervinho), which Mikel Arteta managed to put into the net on the third try (seemingly from an offside position). The Rangers also had their chances, and surely would have tied the game but for Vito Mannone in the Arsenal goal.
In sum, Arsenal were fortunate to come out of this contest with three points. Their problems on offense continue, although at least they started getting some shots on goal after QPR were reduced to 10 men (which they have not been doing in recent matches). Almost as important as the result, it was great to see Bacary Sagna and, especially, Jack Wilshire back in the Arsenal squad.