Shipping estimates for Apple's new 21.5-inch iMac have slipped from previous estimates. Since their introduction, the 21.5-inch model has seen estimated shipping dates of 7-10 days. However, in many European countries, those shipping estimates have slipped to 2-3 weeks.
These shipping delays could be attributed to either an increased demand or trouble with the supply line. An educated guess would put the constraints on the supply side, as demand should be lower now that we have gone through the Christmas season. Estimates for the 27-inch iMac model remain at 3-4 weeks.
Apple has warned that supply could be constrained due to the new lamination process used on the screens. This new process is designed to reduce glare and allow the screen and overall system to be slimmer.