When I enable coverage highlighting, the entire editor's performance degrades significantly. This is most noticeable when scrolling, as the window feels like it is lagging behind the mouse wheel. As it is, I cannot consider dotCover as a replacement for NCrunch simply because enabling highlighting renders visual studio unusable. When I disable highlighting, or open a non-C# file, performance returns to normal. For comparison, enabling continuous testing has no noticeable performance impact at all.
I am running in VS2017, with quite a powerful machine (i7 EE, 16GB, SSD).