We drove from UK a couple of weeks ago and used the ferry from Ancona to Ingoumenitsa, having read loads of horror stories about routes through Serbia and Romania. First day was to Strasbourg, which is well worth the visit in the run up to Christmas. Second day we got to Como after a rather stressful drive across the Alps in heavy snow. Third day we drove to Ancona to catch the ferry the next day. We just turned up at the ticket office and bought tickets on the Anek line, we got a two berth cabin for the price of a two berth . Had a great crossing overnight. The last day was the drive across Greece and to our new home in Sofia. The motorway to Thessaloniki is largely complete, just a few junctions and service stations left to build. If you need fuel then you have to turn into one of the villages beside the motorway. So far they have built the toll booths but not started to use them. They seem to be improving the road from Thessaloniki to the border.
If you have a few days for the journey then I highly recommend this route, just remember - snow chains if you cross the Alps (wish I'd thought of them!) and toll roads in France are not cheap.