I don't follow them, like most of you, but seeing where do they come from and knowing the mentality down there, Olympiacos is your typical rich Balkan team (well, "rich" in Balkan terms) that plays 100 times better in front of the terrifying home crowd, compared to their away matches. Something seem so many times in the past with the ex-Yu clubs, and more recently with the Turkish and Greek clubs.
Their home record in the CL speaks for itself - 8 wins in the last 10 matches, and some of the wins are really impressive (3:2 Atletico in 2014; 2:0 Manchester United in 2014; 1:0 Benfica in 2013; 3:1 Anderlecht in 2013; 2:1 Arsenal in 2012; 3:1 Montpellier in 2012; 3:1 Arsenal in 2011; 3:1 Dortmund in 2011). Only 2 defeats to PSG and Schalke.
On the other side, a pretty poor 2-1-7 record away from home, including that defeat to Malmo some weeks ago.
In a country with lots of internal problems, football is a nice way to take the attention away from the more important issues. The players and the nation will be pumped up ahead of a CL match, especially when a big club comes to town. It gives the players energy and wings.
We know this far too well, and being an Italian team, expect a very tactical and cautious approach, where keeping a clean sheet will be considered far more important than scoring. I don't like it, you don't like it, but that's what's going to happen. Alas, perhaps this time it will work.