"First up; memory usage, it has dramatically decreased, we found
from around 350MB-- when doing normal Internet surfing, watching
large files such as Linux ISOs, etc.-- to around 64MB. Changes add
up to Firefox 3.1 Beta 2 using around only 64% of the memory used
by Firefox 3.0. This let's the browser run much faster.
"The most significant addition in Firefox 3.1 Beta 2 is the new
"Private Browsing" mode, which will not store any of the user's
session information while it is enabled. The feature is similar to
the "Incognito" mode that is offered in Google's Chrome browser and
Safari's "Private Browsing". The feature was first requested for
Firefox back in 2004, but extensive re-engineering was required to
make the feature work."