Why not to use for statistical analysis Excel only?

Excel is cool, I use it everyday. But in case you consider to use it as main (or only) instrument for statistical analysis, working with survey data, etc., I suggest you to read some caveats on using Excel for doing statistics. Here are just some. Just in case, I saved them locally, but you could google them and find more for sure:

• Using Excel for Statistical Data Analysis - Caveats. Eva Goldwater, Biostatistics Consulting Center, University of Massachusetts School of Public Health
  
• Statistical flaws in Excel. Hans Pottel Innogenetics NV, Technologiepark 6, 9052 Zwijnaarde, Belgium
  
• Is Microsoft Excel an Adequate Statistics Package? Practical Stats (PDF copy)