Well one could always update the Safari engine yourself without waiting for apple. Safari uses Webkit which is Open Source 
and most issues are patched in the open source version before they are fixed in the Official Apple Release
The webkit site has prebuilt binaries for both Mac OS X and Windows of the latest version:
http://webkit.org/
Also if you choose about Safari you can see what version of webkit apple is using, the webkit version is beside the safari version
Example: Version 3.1.1 (5525.18)
when you install webkit it launches using the Safari front end using the updated engine (you have to have Safari installed).