Our company needed a Silverlight grid that could provide control over every detail of the display of every individual cell, including Excel-like formulas. Syncfusion's Essential Grid for Silverlight provides that. It has good performance and a full featured API that allows many ways of filling it with data. When I've had questions or issues, the Syncfusion support has provided responses in a timely manner. I would recommend it for anyone that needs a powerful, flexible, cell-based display.