Hi Daniel -
At the time of NCrunch's first beta release, VS2008 was already a fading memory, with very few users still making use of it. One of the big issues with VS2008 is that it uses a completely different UI structure to all later versions of Visual Studio, which meant that certain NCrunch features (such as marker customisations and the corner spinner), would need to be built twice in order to support this older version. As both these features were implemented well after the VS2010 release, it simply wasn't feasible to repeat the work for VS2008 as the cost would be 3x as high (WPF made these features much easier) and less than 2% of the NCrunch user base would see any benefit from it.
So I'm afraid that this is by design (see
http://www.ncrunch.net/support/frameworks for the official line). NCrunch does still work with VS2008, but there are limitations around some of the UI features that you're likely to notice if you're downgrading from a later version of Visual Studio.
Cheers,
Remco