== Radix-based sorting == 

 I've updated the performance summary to be accurate for both LSD and MSD radix sorting.  For MSD I picked an "in-place" sorting approach (which is not stable), to differentiate from LSD radix sorting. 
 I also have added Spreadsort performance info.  Spreadsort actually has two worst-case performances (the one mentioned, and O(nlog(n)), and its worst-case is the better of the two, but I put in the version that applies for large n and reasonable k, as I figure that is more relevant to an asymptotic discussion.  It's worth mentioning that in certain modes of operation, Spreadsort is basically an MSD radix sort where s = log(n)/c, and c is a constant, though it also does comparison-based sorting to obtain better worst-case performance and better performance on random data.