Hi Ilya,
Thanks for reporting this. We have restructured some internal code for the next maintenance release that will allow this to work by using code below instead:
<grids:PropertyGrid.ItemContainerStyleSelector>
<grids:PropertyGridItemStyleSelector>
<grids:PropertyGridItemStyleSelector.PropertyStyle>
<Style TargetType="grids:PropertyGridItem">
<Setter Property="Visibility" Value="{Binding IsVisible, Converter={StaticResource BooleanToVisibilityConverter}}" />
</Style>
</grids:PropertyGridItemStyleSelector.PropertyStyle>
</grids:PropertyGridItemStyleSelector>
</grids:PropertyGrid.ItemContainerStyleSelector>
Note that we use an ItemContainerStyleSelector for picking the PropertyGridItem Style because it can be one of three styles (category, category editor, or property). By using the code above (starting in build 651 only), it will allow you to alter the property style while leaving the others in tact.
We're not sure when build 651 will be ready for release since 650 just came out, but if you'd like to test a preview build, please write our support address and reference this thread in your email.