Nautilus underwent several changes between versions 2.4 and 2.6; most notable is the change in the default browsing method. In 2.4, the file manager used a "browse" view similar to using a Web browser; all folders opened in the same window, and it could be used to view files as well. GNOME 2.6 uses a spatial interface by default, which, in essence, makes the window the folder. Each folder opens in a separate window, and this window remembers its size, position, and even location in the file listings.
Some users of GNOME dislike the new interface; it is easy to switch back to the old one by using the Browse Folder command, or by using the GConf editor to force these changes in the file manager by default. To do this, open gconf-editor, open /apps/nautilus/preferences, and check "always-use-browser".
A "Computer" icon has also been added to the desktop, which shows disk drives; network computers; and remote FTP, SSH, and WebDAV servers.
The file chooser dialog was completely revamped, replacing the older, harder-to-use version with one resembling the Windows XP file dialog. The newer window shows the path to your location as a series of clickable buttons that will bring you back to that directory. One con of the new "open" dialog is that it no longer allows the user to type in the filename, however.