Xceed announced today their FREE datagrid for WPF ... Check it out here http://xceed.com/Grid_WPF_Demo.html
It looks neat.. groping, sorting, styling, editing , data binding, etc.. (disclaimer: only ran xbap, I did not download and play with it yet ... I did like the demo itself )..
Did I mention it is FREE!!
WPF is really gaining a lot of momentum lately, dont you think?