I've been experimenting with multicamera editing in VP8. However I don't see a way to see how the transitions look when editing from the multicamera track since the preview window is occupied with the multi-views.
""Show Full Frame on External Monitor" is what it's called at least in VP13, not sure about VP8. It should be under "Tools -> Multicamera"."
Off course it requires external monitor, (or two, if you have large number of cameras and Vegas preview window is just to small to see details once split into so many tiny windows) - but for this purpose alone it would be money well spent. Constant toggling to and from the MC view is not very efficient, and disturbs your mood and tempo while picking takes, especially in music video.