Looking at the stats for Jan/Mar 2008 Nice was 55/60 with lows of 40/45 at night whilst Rome was 60/65 with lows of 45/50 but on a few days it dropped to -2. The weather doesn't start picking up until May and you could have quite choppy waters in the Jan/Mar period. You don't say east/west Med but certainly warmer in the east but no way of escaping the choppy seas, I would be looking at the Caribbean at that time of the year and thats where we will be in April, 2009 with temps in the low 70's.
There is a big difference between the West Med and the East Med the better and warmer weather being in the east. The time of year you are suggesting you can expect it to be cold and often stormy the later in the year you can leave it then the better. ... Ida.