They might have borrowed from R. Wes McKinney admits to being influenced by R especialy data frames...but it makes data analysis all the more easier when i can do everything i want within the the Python environment. pandas is proving to be a bit of a longer learning curve i must admit, but then the python environment and native Matplotlib support made life oh so much simpler.

That's just me though.

What has pandas borrowed from R, other than a 2D data structure with heterogeneously-typed columns?

I guess the data frame merge invocations are similar.

(I know patsy/statsmodels are introducing R's formula syntax to python, but that's not pandas.)

The split-apply-combine framework dealing with group by tasks (http://www.jstatsoft.org/v40/i01/paper, not that there aren't other precedents) for one. But generally, Wes has used R to figure out what people want to do, and then ported an elegant interface to python.