If you've heard of Xceed's free datagrid for WPF, here's some news:
Microsoft has just published a Channel9 video in which Adam Kinney
interviews Pascal Bourque, the lead developer of Xceed DataGrid for
WPF. Pascal talks about what it's like to develop a rich control using
WPF, and also previews one of the upcoming 3D views.
The video on Channel9 / MSDN is here:
I hope you enjoy it.