When using new rich:column's sortBy attribute it improperly treats all data as Strings when performing sorting comparisons. So for example in case of ascendant sorting of two integers, "10000" will improperly appear before "9". Why don't you just use Comparable methods for values which implements this interface?
Inability of using Dates, Numbers etc. renders sorting functionality quite unusable in real world applications.
Looks like Scrollable datatable is subject to this issue, too.