The pelican cases are popular with some who want to carry camera or computer gear. I used to have a very small case mounted to hold my SLR.
The problem with the Pelican case (in my opinion) is the ratio of internal space to external space. The thickness of the case plus the various ribs, etc., make the inside too small for a given external volume. That and I prefer not to use top cases in general.
Some use the Pelican cases as panniers, too. See http://cariboucases.com/