Thunderbird & OSMO make a good combination. But you add in skype, and maybe a few other things, and you have fractured contacts list.
Since OSMO is really a PIM pretending to be a calendar, my opinion is the PIM should be taking the lead in managing contacts. I see a few people requesting calendar synchronization. But in order for everyone to stay roughly organized, I would like to hear from OSMO authors on what they think the options are NOW, and going forward.