I am a big fan of Resharper. It helps me be more productive and that is better for me and my company. One thing Resharper does is line highlighting in your IDE. So whatever line you are on will stand out. But I decided to try a dark theme with Visual Studio recently and I could hardly read the highlighted line. I turned off that feature in Resharper and everything cleared up.
As you can see the Resharper v3 highlighting is terrible looking against a dark background. I don't know if there is a way to fix it in Resharper but I haven't found a way.
A Free Solution
I have another addin called SlickEdit Gadgets v2 for Visual Studio. It has several nice features such as line highlighting, a ruler, a vertical line called an indentation guide and a very handy Command Spy which tells me what shortcut keys are available. Best of all IT'S FREE!!!
As you can see the Visual Studio theme is dark and line 97 is highlighted. It looks great even in this dark theme. Also, the indentation guide is visibly showing the alignment of the code. Try it out for yourself and I think you will like it too.