In my opinion the lack of decent design-time tool support is currently hampering the adoption of WPF, that and the relatively small number of controls available to the developer out-of-the-box. The later is being addressed to a certain extent by the developer community, notably by Marlon Grech's Avalon Controls Library and the WPF Toolkit. The former, design-time support, is something that is harder for the developer community to address, however Karl Shifflet's XAML Power Toys, which add drag and drop form generation make a pretty good stab at it.
Despite this, people are adopting WPF even though it is not RAD yet.
However; there are interesting developments at Microsoft, a video on Channel 9 reveals that Drag-Drop Data Binding will com to WPF in Visual Studio 2010. Exciting news indeed!
The screenshot below shows a Window which contains two ListViews in a master-detail configuration, which was entirely developed by drag and drop (minus a few code tweaks due to minor bugs in the VS 2010 CTP):
The demonstration details how DataSets, ADO.NET Entities, or Objects can be bound - with master-detail view achieved by 'chaining' CollectionViewSources, in the same way that you would a Windows Forms BindingSource. All this will sound familiar (and cosy) to a Windows Forms developer.
I am guessing that VS2010 will also provide the same drag and drop support for the WPF DataGrid.
While this looks like excellent news, drag and drop is not the be-all and end-all of RAD application development. Once you have dragged your UI elements onto the Window you would also want to be able to re-configure the source of the bindings, or the bound properties without having to touch the XAML. I do hope that VS 2010 brings this functionality also.
Either way, VS 2010 should open up WPF to a whole new audience.
Regards, Colin E.