I always rent lenses for a good couple of weeks added up before investing in one. This is one of my dream lens, and been lurking sites for weeks trying to buy one, ts been out of stock for a while. So I figured the stock notice might be useful for others too.
Amazon.com (US) has some in stock right now. For the past few days, they have listed 10 in stock as ships from/sold by Amazon at a price of $3115, which is $316 over Canon's MSRP. A couple of hours ago, I noticed the price had dropped to the proper $2799 still showing 10 in stock, and 20 minutes ago they showed 3 in stock. Then I ordered one, and it's now showing 2 available. Act fast and good luck.