From the Beeb
From optajoe on Twitter: "Nicolas Anelka was top scorer in the Premier League last season with 19 goals - Rooney has 20 already in 2009/10. Golden."
BBC Radio 5 live's Lee Dixon: "United have flooded the midfield and hit them on the break - the gameplan is perfect so far. That second goal really is one to remember and Wayne Rooney was just brilliant in it."
1648: Half-time Arsenal 0-2 Manchester United
What an incredible period of play that was. Arsenal had looked the likelier to score, but they are going to have to produce the performance of the season to get anything from this. Two-horse race?
1647: Nice run forward from Alex Song and he's set up by a flick from Cesc Fabregas, but the Cameroon midfielder drags a left-foot shot wide from 12 yards.
1644: NO I'M NOT A UNITED FAN BUT THOSE GOALS WERE STUNNING.
BBC Sport's Phil McNulty at the Emirates: "Manchester United have just taken Arsenal to the cleaners in two moments of brilliance - and Nani has justified his selection with a blistering display, forcing Manuel Almunia to palm into his own net after a run Cristiano Ronaldo would have been been proud of and setting up a second for Wayne Rooney. Nani has been erratic so often, but this is end product par excellence. And Rooney sprinted from deep inside his own half to finish the second. Arsene Wenger is slumped back in his seat - and no wonder."
1641: Has to be 0-3. Wayne Rooney does brilliantly to persevere down the United left and eventually beats Alex Song to get a cross in. Paul Scholes keeps his cool to tee up Nani 12 yards out and he drills wide of Manuel Almunia's right-hand post. Should've scored. United are electric.
1641: See 1638 - I meant Champions League semi-final. I was over-excited.
1640: Wayne Rooney has just scored his 100th Premier League goal and Arsene Wenger looks like someone has just punched him in the stomach. Hard. Andrey Arshavin has a great chance 14 yards out, but fires wide. Mountain to climb.
United goal: Sometimes you have to just stand up an applaud. That is as magnificent a goal as you could wish to see. United break with alarming pace - it's like last season's Champions League final all over again.
Wayne Rooney starts it just outside his own box, feeds Nani and then the pair both sprint forward - they get to just outside the Arsenal box and Nani tees up Rooney to sweep a devastating blow past Manuel Almunia. What. A. Goal.
1638: GOAL Arsenal 0-2 Manchester United
1637: Arsenal take a quick corner and Cesc Fabregas hammers the ball across the face of goal from their left - Wes Brown gets a crucial touch at the far post.
1635: What a goal. That's the inspiration this game was waiting for - and another surprise selection from Sir Alex Ferguson is vindicated.
United goal: That is genius. Move over Ronaldo, there's a new wing king in town. Nani keeps the ball in down the right and beats two players with a majestic flick between his legs. He dummies his way past Cesc Fabregas who cannot make a tackle in the area and lifts the ball to the back post, where
Manuel Almunia can only tip it into his own net. Not great keeping, but stunning from the Portuguese.
1633: GOAL Arsenal 0-1 Manchester United