R is not at all like Excel, in form or function. R is actually a complete programming language, much more similar to Python in that respect. It supports two types of OOP (S3 and S4), has hundreds (if not more) of contributed packages that do things like survival analysis, 2D/3D plotting, bioinformatics, machine learning, Bayesian statistics, econometrics, numerical integration, spatial statistics, and more (http://cran.r-project.org/web/packages/)

One major advantage over Python is that it's vectorised, so you can say things like A + 1 when A is a vector (or matrix). A bit like Matlab in that regard, only that it doesn't suck as much as the Matlab ``language''.