R is the tool for choice for serious statistical analysis. It's not an easy platform, however, and learning takes some time. The good side is how powerful it is for *any* type of analysis, data, or problem. The help support is very good and user forums are very active and helpful. This is not the package of choice if you are doing sporadic data analysis, but I'd recommend it to anyone seriously involved in statistical analysis. If you are just starting with statistics and plan to keep doing data analysis- go for it. If you are using other packages and statistical analysis is a major part of your study, go for it. No other package offers the versatility and support R has. If the command line mode is really intimidating to you, you can use the R-Commander GUI (just install the Rcmdr package), but the real power of R lies in its command-line. You can run R with the binary cocoa application, from the Terminal, within emacs, or within TextMate.