Eintracht Frankfurt made it three wins out of three and spoiled Rafael van der Vaart's second Hamburg debut as the newcomers won 3-2.
Armin Veh's men signalled their intentions with two goals inside five first-half minutes from Takashi Inui and Olivier Occean.
Hamburg pulled a goal back on the stroke of half time through Heiko Westermann, but they also lost Petr Jiracek to a red card before the interval.
Aigner gave Frankfurt a two-goal cushion to sit on in the 52nd minute, but Heung Min Son made a game of it by scoring a second for Hamburg in the 63rd minute, setting up a tense finale in which Frankfurt held on to join Bayern Munich in a share of top spot.
Freiburg got the better of Hoffenheim in a 5-3 thriller at the Dreisamstadion, with the pressure increasing on the visitors' coach, Markus Babbel.
The game started well for Hoffenheim with Matthieu Delpierre putting them ahead in the second minute, but Karim Guede and Max Kruse turned the game around before half-time. Boris Vukcevic brought Hoffenheim level in the 57th minute before Fallou Diagne headed Freiburg ahead for the second time.
Hoffenheim refused to lie down and they equalised again through Takashi Usami in the 76th minute, but Cedric Makiadi and Sebastian Freis ensured Christian Streich's side were ultimately rewarded with all three points.