Apple has refreshed their iMac series with all new Haswell processors along with updated graphics capabilities. The 21.5 inch model has a integrated Iris Pro and the 27 inch model has an Nvidia GeForce 700 series graphic card. Both can be upgraded.
Apple also says that their Fusion Drive option will be improved as well. They say that speeds will increase by approximately 50%. The new iMacs are available today starting at $1,299 for the 21.5 inch model and $1,799 for the 27 inch model.