Hello,
I already developed in the past with your WPF controls and I'm mostly very happy. The controls are nice and the programming model (MVVM) is well done. I always recommend your controls the all my friends developer out there.
For a new project, I'm evaluation the Report Design + Viewer and I must say I'm very disappointed by the all product. 
First the general looking and feel seems coming from an old Visual Basic 6 age with outdated button toolbar + gui; non sizable dialogues like the one to choose fields (attached) With data source coming from entity model, the field and navigation property are often long and this is painful and useless to scroll horizontally to see the field name.
Coming back to data source, the report wizard is also confusing asking for an data source name rather than asking for an existing connectionstring and then create a new one for your need internally if needed. Also, the experience with an existing data model object is poor because the Data Member question is not obvious and when I select one the entity table, the wizard prompt with an alert see capture attached. If I don’t select any member, no alert but the field list is useless because I don’t see any field (see capture).
In conclusion, it seems to me the Report components are not done by the same team or at least are not develop in the same spirit and quality than the other controls.
I hope you will bring us a brand new controls asap.
Thanks for reading me 
Best regards
-Vince