I only have one device, and I'm using stock PR1.3, so I cannot test against the CSSU or power kernel (or any of those tweak/hack scripts).
Preview playback is possible. I tested it a while ago, but decided to leave it out for now. I'm not sure about reading comments etc, as these would need to be loaded during playback if you are not launching from the video info window, which could interrupt playback on slower connections.