With
SetDirectory["~/Downloads"]; ifile = "test.xls"; TimeConstrained[idata = Import[ifile, {"Data", 1}], 5]; I can achieve the desired result of importing the first page of the spreadsheet in under 5 seconds.
When the same data are reformatted (Excel "Save As ...") to ODS format
SetDirectory["~/Downloads"]; Clear[idata]; ifile = "test.ods"; TimeConstrained[idata = Import[ifile, {"Data", 1}], 60]; times out.
Is ODS Import[] broken? Does anybody else have this issue?