IMHO, WPF can already be used for LOB applications, but of course, as it is very new environment, there are still some missing features (datagrid, common control such as a date picker…). Karl Shifflett did a great work on building a LOB application to demonstrate how we can leverage the power of WPF for that kind of application. You can find the blog post here: http://karlshifflett.wordpress.com/2008/05/16/wpf-multi-tier-business-application-track-code-camp-source-code/

There is a lot of skepticism about WPF. Some people have gone to the extent of declaring it not ready to build line of business applications.

After watching Billy Hollis demonstrating a really nice and very well-designed WPF application [See Dot Net Rocks TV Episode 115 - http://www.dnrtv.com/default.aspx?showNum=115, the first 25 minutes of the video is enough], I started working on a music catalog application in WPF. Much of it was inspired by what Billy said in the presentation.

What you write above is perfectly valid and to the point. WPF gives designers and developers a whole new way to design and develop really neat, effective user interfaces. It is different way of thinking. I have come from VC++/MFC days, through ASP.NET 1.1/Winforms, then ASP.NET 2.0/Winforms again, and, landed straight to WPF!! So, I can appreciate the whole idea of separating the presentation from the code-behind.

My two cents.

Cheers,
indyfromoz