Dawn,
 
Mostly our finance dept uses it to reconcile inventory transactions that went really goofy.  They'll also use it as a sort of diagnostic tool (report mode) to see what will happen with a given issue.  Of course, running in report only takes just as long as running the real deal, so they resort to this util only when nothing else will fix the problem since they basically have to kick everyone out while they run the util.
 
Val

We have used it here when we have had some thingsgo awry with inventory.  I would recommend always running it in report only mode first and then examine what it wants to change.  When you try to run if for a single item or range, it still seems to grind through the whole inventory files.
Also, we had a situation once where after running it in 'make the changes' mode, it created inventory entries in locations that we had previously consolidated and deleted (i.e., querying a indivdual inventory item showed more than one location, but the location did not exist in the location master file).