I have been using the excellent information from the forum to research catching an overnight ferry from Naples to Sicily. I want to know if it is reasonable to just turn up and buy a ticket or should I book ahead. We are travelling early January 2010.
Thanks.

You should be fine by buying on the day of departure, certainly after January 6.

GAC - thank you, I was hoping you would reply as you have previously put some great information up. We want to cross on the night of the 2nd .. you think it will be fine to just turn up at the terminal?

There are two companies running to Palermo (SNAV and Tirrenia). You will certainly be able to get on a ship but, if the ship is busy, you may not get the accommodation you want.
On 2 January, the ships are more likely to be busy FROM Sicily TO the mainland, as people return to work or study after spending the holiday with their families.

caitg: you can check availability of cabins and recliners for both SNAV and Tirrenia by pretending to make an online reservation. Today, both operators show wide-open availability every day for a week around January 2, 2010. I note from the Tirrenia site that January 1 and January 3 have "high season" fares, probably because they fall on a Friday and on a Sunday.

These are the odds: the two ships have a total of 600 cabins. What are the chances that there will not be a single free cabin on Saturday, January 2? Worst case: you'll end up in a reclining seat for the 10-hour crossing: no worse than being on a transatlantic flight (indeed, much better). My advice: try to buy the tickets when you arrive in Naples. If this is simply not possible, I nevertheless think that buying on the day of departure is a risk worth taking. NOTE: the first class recliners on the Tirrenia ships are supposed to be quite comfortable. According to the Tirrenia website, on January 2, the ship will be either the Florio or the Rubattino (with 195 first class recliners and 289 cabins).

Thank you both for your replies. It makes planning travel so much easier when people are willing to make their knowledge and experience available to others.