higher moments of entropy... does the variance of $ \log x $ have any operational meaning?
$\log 1/x_i$ is sometimes known as the 'surprise' (e.g. in units of bits) of drawing the symbol $x_i$, and $\log 1/X$, being a random variable, has all the operational meanings that come with any random variable, namely, entropy is the average 'surprise'; similarly, higher moments are simply higher moments of the surprise measure of $X$.
There is indeed a literature on using the variance of information measures (not of surprise in this case, but of divergence), here are two good places to get started on a concept called 'dispersion': http://people.lids.mit.edu/yp/homepage/data/gauss_isit.pdf http://arxiv.org/pdf/1109.6310v2.pdf
The application is clear. When you only know the expected value of a random variable, you know it at first order. But when you need to get tighter bounds you need to use higher moments.