Well, if you want to "divide" your screen while browsing for files or want to start terminal within the File-manager itself or bulk renaming your files with ease, etc... then Double commander is a very powerful utility.
*. Tabbed interface.
*. Built it Terminal command window.
*. Multi rename.
*. Powerful internal text editor.
*. Handles archives without third-party utilities (ZIP, TAR GZ, TGZ, LZMA and also BZ2, RPM, CPIO, DEB, RAR.).
|Powerful built in options of its own!...|
*. Since it's based on the Total commander (another powerful file-manager), it supports a lot of it's plugins as well.
So if you run Ubuntu 10.10 then you can easily install Double commander by issuing the below command in your Terminal (using a PPA channel).
sudo apt-add-repository ppa:alexx2000/doublecmd
sudo apt-get update
sudo apt-get install gtk-doublecmd