I just released version 0.5.0 of dvswitch, the software DV mixer intended for use at DebConf 7. I believe I've met all of the video team's essential requirements and most of the desirables.

Unfortunately real video mixing seems to take a faster machine than I have at the moment and I very much doubt I'll have time to improve that much. Although I have implemented picture-in-picture mixing, it won't be usable and may result in frame dropping, so I've started a stable branch intended for DebConf 7 that doesn't include it. Version 0.5.0 is released from this branch and can be considered the first alpha test version. There's now a little over a month to test, fix bugs and make minor improvements on this branch.