Gnumeric
Gnumeric is a powerful spreadsheet application which can import and export in various formats including csv, HTML, LaTeX, Lotus 1-2-3, OpenDocument Spreadsheet and Microsoft Excel.
Installing
Install gnumeric from the Official repositories.
Optional dependencies are psiconv (for Psion 5 file support), python2-gobject2 (for python plugin support) and yelp (for viewing the help manual).
decimal separator
Gnumeric is depending on your locale and use it for exporting as csv file too. For example, octave use dot decimal seperator.
Display 1/2:
With german locale "de", Gnumeric shows 0,5 (comma)
With englisch locale "en", Gnumeric shows 0.5 (dot)
To start Gnumeric with a different locale, just run
LC_NUMERIC="en" gnumeric