I attended an intro to R workshop and found it very confusing. Being "functional" had nothing to do with it. Inconsistent, yes very much so in my opinion. It felt like a lot of little separately developed tools thrown together into a bundle. But I think mostly my difficulty with R is that I'm not a researcher or statistician. My exposure to and experience with those domains was an undergrad class or two many decades ago. If you don't deeply understand the problem space for which R is intended, you will be lost and confused trying to learn it.
It's a very different language to imperative languages out there, so it's not surprising that an introductory course would be confusing. There are several ways to do things in R (for example subsetting data, or pulling out elements of structured data), but that doesn't mean it's inconsistent - they are convenience functions. As you say, you have to do some statistics 'in anger' to really get why R is so good. When I've taught introductory sessions on R I focus more on a very short analysis to demonstrate what it is good at.
