According to Microsoft, almost half of all PCs running Windows 7 are running 64-bit editions of the OS.
This information from the Windows Team Blog:
Are you running a 64-bit edition of Windows 7? There is a high likelihood you are. As of June 2010, we see that 46% of all PCs worldwide running Windows 7 are running a 64-bit edition of Windows 7. That is, nearly half of all PCs running Windows 7 are running 64-bit. Compared to Windows Vista at 3 and a half years after launch, only 11% of PCs running Windows Vista worldwide are running 64-bit. With Windows 7, running a 64-bit OS is becoming the norm.
What makes really interesting reading is the breakdown of 32-bit/64-bit for XP, Vista and 7:
The reason for the low 64-bit take-up of XP is clear enough to anyone who tried using it - the experience sucked. On most systems you'd be lucky if you found all the drivers you needed to actually get the system set up correctly, let alone get your software apps to work.
The main benefit that users see from adopting a 64-bit platform is the ability to break the 4GB memory barrier, which means they can fit more RAM, which in turn means snappier performance and the ability to run more applications concurrently. Other benefits include improved security and support for virtualization.
64-bit adoption of Window 7 is incredible, but I can't help but feel that the number might have been even higher is if Microsoft had given 32-bit OS users an easier upgrade path rather than to have to perform a wipe and reinstall.
32-bit is certainly being handed its hat ...