Apple's skeuomorphic design for iCal is bad. iCal has been made to look like a real calendar, but in reality it isn't used like a real one at all.
If iCal worked like a real calendar, skeuomorphism would have value, but in its current form, it's just an ugly skin. It doesn't actually show users how to use it.
Read about it here: http://arstechnica.com/apple/reviews/2011/07/mac-os-x-10-7.a...