my test drive of a 64 bit slack distro
 

bluewhite-64 well so far it's slackware the exact same set up as slack

except
configure scripts scroll by so fast that there is no hope at all
of reading any thing but the last page

bzip2 works as fast on 64bits as gzip works on 32bits

switching between browser tabs is noticeably faster

building and installing the wifi modules was almost instantaneous

programs start up faster

boot time is about the same (a little faster but not by much)

over all the computer the computer is 2 to 3.5 times faster

installing browser plugins is more work (the 32bit ones need niswaper)

over all I'd say if your chip set and CPU are made for 64bit operation
go for it
it's worth the little extra work for the performance gain

Been using a 64-bit distro for almost three years. Surprised you notice a difference with such mundane tasks as unpacking a tarball and switching browser tabs. I always find it interesting that people use wrappers for browser plugins. Completely unnecessary if you simply use a 32-bit browser. I'd agree that if you have a 64-bit machine, use a 64-bit distro.