A notable omission from the controls available in the first release of Windows Presentation Foundation is a datagrid. Component vendor XCeed has stepped up with a free WPF datagrid. Registration is required, but Xceed says:

The free license is a perpetual license and includes royalty-free distribution, bugfixes, and new features, so your company can use it with full confidence.

Paying customers get support along with an option for source code.

I’ve not tried the control yet, but if you are experimenting with WPF, it strikes me as worth a look.