Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
One thing that frustrated me the most with Firefox 2 was trying to view security information for individual sites.
You had to look in multiple locations to view cookie, password and permission information for a site, where some of the information is mixed together with other sites. Or, end up degrading performance on Windows computers by using using add-ons to accomplish the same task.