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".
• NoSharedFormulas - this experimental feature enables writing of workbooks without using the shared formulas feature of .xls, .xlsx and .xlsm. This may improve the calculation performance of Excel with certain workbooks. Unfortunately it will cause written workbooks to be larger and will slow down reading and writing these workbooks in SpreadsheetGear and Excel. At this time it is not clear whether this feature will eventually be removed 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 "NoSharedFormulas".

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

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

IWorkbookSet Interface
IWorkbookSet Members