Mihai Ciuca , Jan 11, 2010; 01:19 p.m.
I don't have experience with that Sigma but I tested a Tamron 17-50/2.8 VC. This is around $650 new and is a very good option. The VC (equivalent of VR) is very efficient for taking images handheld and the lens provides sharp and pleasant images. On the other hand, 17-50 is a better range on crop camera than 24-70. This particular Tamron is one of the best lenses from Tamron's lineup. You cann't go wrong for this ammount of money.