In general, the motherboard is not an important factor in video editing, the cpu is. As an exception, I think there are some features of the H67 sandy bridge chipset that enable quick sync which accelerates video editing. The upcoming Z68 chipset will also allow quick sync. You need to do some searches for benchmarks using your editing software.
^+1 regarding Quick Sync, it accelerates only the H.264 MPEG-2 & MPEG-4 encoding - the software/plug-in support is currently limited. If you are going to be using Adobe Premiere then there are specific GPUs that allow acceleration in addition to the plug-in for Quick Sync.
IMO - Wait the 2~3 weeks for the Z68 MOBOs, the information 'today' is very limited so it's impossible to recommend a specific MOBO. However, I would look at the i7-2600K CPU if your App supports Hyper-Threading.