Practical Applications of Radix Sort
Radix sorts are often, in practice, the fastest and most useful sorts on parallel machines.


Zagha and Blelloch: Radix sort for vector multiprocessors. Supercomputing, 1991: 712-721.
Blelloch, Leiserson, Maggs, Plaxton, Smith, and Zagha: A Comparison of Sorting Algorithms for the Connection Machine CM-2. Symp Parallel Algorithms and Arch (SPAA-3):3-16, 1991.
Arpaci-Dusseau, Arpaci-Dusseau, Culler, Hellerstein, and Patterson: High-performance sorting on networks of workstations. Conf on Mgt of Data, (SIGMOD-1997):243-254.
Arpaci-Dusseau, Arpaci-Dusseau, Culler, Hellerstein, and Patterson. Searching for the sorting record: experiences in tuning NOW-Sort. ACM Sigmetrics Symp Parallel and Distributed Tools, (SPDT-2):124-133, 1998.


On each node of the multiprocessor you probably do something like a quicksort, but radix sort allows multiple nodes to work together with less synchronization than the various recursive sorts.

There are other situations too.  If you need a stable sort (a sort where whenever two keys are equal they stay in the same order rather than getting rearranged) then I'm not aware of any version of quicksort that will be of use.  Mergesort is also stable (if implemented correctly).  Your link is the first time I've ever heard anyone say that mergesort could be made to have better cache behavior than radix sort.