You can force Chrome to update to this by going Chrome > Tools > Extensions > Developer mode > Update extensions now.
Notes are below, but really it's just a spruce-up with an emphasis on calculating Standard Data and Free Data together in places. A couple of new options are enabled by default on the Options page... The new "Total Data Used" option probably makes Free Data Used and Standard Data Used redundant now!
v1.4.0 - 6 January 2013:
Added pop-up and tooltip options for Total Data Used; this is the equivalent of Free Data Used + Standard Data Used.
Added pop-up and tooltip options for Suggested Daily Usage.
Percentages and estimations are now calculated based on Total Data Used instead of Standard Data Used.
You can now hover over an option on the Options page to see a detailed explanation of the option.