I bought D:OS through steam and the steam cloud sync worked great.  No matter which OS I played on, when I rebooted and start up in the other OS, all the game saves were there.  I was even able to take my Mac saves, start up boot camp, steam cloud sync, run a save game editor, start up Steam to re-sync to cloud, then go back to Mac and the edited save was there.
I wish there would be some news on the D:OSEE Mac front.  Even something like we're behind schedule so expect it next year would be nice.  I've been playing in Windows through Boot Camp, but I prefer to stick to the Mac side so I'd like some idea of how long I'll be limping along like this.