Users are starting to report significant shipments of PowerMac G5 2.0GHz machines. Many have received them, and others note that Apple Stores have already started receiving them.
Both the Apple Store at The Grove in Los Angeles, CA as well as the Stanford Bookstore have had shipments which were available to the general public. (Note: you must be affiliated with Stanford to purchase from them)
MacUser.co.uk also notes that UK 2.0GHz G5s are also shipping.