It was not hard to guess that the discounted Windows 7 Upgrades would sell like hot cakes. Microsoft is after all giving about a 50% discount on the new Windows for owners of a Windows XP or Windows Vista license.
The $49.99 Microsoft Windows 7 Home Premium Upgrade is leading the software sales charts on Amazon.com followed by the Microsoft Windows 7 Professional Upgrade selling for $99.99.
The discounted Windows 7 pre-order offer ends July 11th. Some say there will be discounts after this date, but I would not bet on it.

I also guess Microsoft will soon announce a mind blowing number of Windows 7 pre-orders. If you plan to keep your current hardware and want to upgrade to Windows 7 you really should not take any chances and pre-order now.