Improving Firefox with Private Browsing

Now with v3.5 out, can Improving Firefox Portable's Performance be updated to replace "Disable Cache" and "Disable History" with Tools=>Options=>Privacy=>Use custom settings for history=>Automatically start FireFox in private browsing session?

Also, privacy aside, does it make the actual browsing faster or slower?

And is it also technically safer (like a sandbox)? Or is it nothing more than a "delete history on exiting" setting?

Thanks!