The video feature is absolutely fantastic. However, one major nuisance is the fact that you can't (at least to my knowledge) start the preview sequence from a given point in the timeline. When I'm modifying my keyframes I'd like to be able to start the preview at a point close to the frames that I changed. However, the preview always starts from the beginning. I'm currently working with a walktrough through a hospita (in Revit)l, that is about 8 minutes in length, and it is very annoying having to watch the whole video to see changes I do to the end of the sequence.
I think you can with a short-cut key... if you are in the "Keyframe editor" (where you move/edit specific camera points) you can just hit [P]
(If you hit the "preview" button from the "Video editor" it will play from the start)
Gadget already mentioned what you need to know about the usage of the "P" key when you're in any keyframe of your desire. If this is already sufficient to you, let me know, otherwise kindly also let me know if you'd like me to file a corresponding feature request regarding this subject, in case you have any further feedback regarding how we could improve the usability of this kind of preview functionality even further.