I'm a happy plain TeX (and XeTeX) user.
I recommend everybody to study the TeXbook by Knuth, even LaTeX users. It's wonderfully written and teaches you the concepts behind the typesetting decisions of TeX.
My motivation here is to try to solve problems using techniques available for plain TeX, so no such thing as "you should use this package to solve the issue of that other package" and so on. I value simplicity and elegance above all -- that doesn't mean I can achieve them though :-)
Q&A for users of TeX, LaTeX, ConTeXt, and related typesetting systems