The differences, although noticeable, are really subtle (with the exception of the front and rear facias). Saw one on I-5 in Southern California last weekend just over the Grapevine and followed it for about 10 miles. Had New Jersey plates, and was the Modern Line in Mojave Metallic paint with the 19" double spoke (401) wheels. Looked very nice on the road.
Past: 2004 E46 330ci Convertible
Present: 2008 E93 M3
Present: 2012 740Li (F02) M-Sport (European Delivery)