I realize this is very late but for the few visitors out there who are not aware, Mew is available for download over the Nintendo WiFi connection.
Players with Pokemon HeartGold Version or Pokemon SoulSilver Version can download Mew between October 15 to October 30 so that leaves you with 2 more days to download this mysterious, rare, Psychic Pokemon!
The Mew you will receive is a Level 5 and comes with one basic Normal-type attack, Pound, giving you the ability to raise and train Mew as you see fit. Making this distribution especially exclusive, Mew comes inside a Cherish Ball and has a Premier Ribbon, both indicating that you got it via a special event.
I downloaded mine 2 days ago. It feels so good to finally have a legitimate Mew!