Currently, there is one publicly documented experimental feature in SpreadsheetGear:

• OleDbOpenXmlWorkaround - this experimental feature enables writing of Open XML workbooks which the OleDb provider can read. As of May 2009, the OleDb provider does not fully support the Open XML file format and will not read workbooks written by SpreadsheetGear unless this experimental feature is enabled. At this time it is not clear whether this feature will eventually be removed (because OleDb has been fixed to read compliant Open XML workbooks) or whether this feature might find it's way into a permanent API. Any change to this experimental feature would only be made in a major release of SpreadsheetGear. To enable this experimantal feature, set this property to "OleDbOpenXmlWorkaround".

Once an experimental feature has been enabled for a workbook set, it cannot be disabled.

Reference