Greece is the Word

Yes, yes, Syriza is a bourgeois reformist party which has drifted to the right even in the last few years.  I know.  A Syriza victory will not bring full communism in Greece.  No, true.  A Syriza government will cave in and give up all over the place.  The way all bourgeois reformist parties always do, even quite Lefty ones.  Yes.  I know.

I knows and knows and knows. 

The point is that, as with all Left-wing reformist parties, it will be as strong or as weak as the movement among the working class.  It will be pushed to the Left by a genuine movement on the streets and in the workplaces.  Or to the Right by the absence of such a movement.

The anti-reformist gloom of writing off Syriza before it starts is, paradoxically, the gloom of the reformist.  It is the gloom of those who secretly expect (or want) elected governments to do it all for them.

A Syriza victory would create a space within Austerity neoliberalism for a challenge (however partial and bourgeois and reformist and imperfect) to the prevailing, even suffocating, orthodoxy.  The punishing flow of weath upwards may be slowed, just a bit, just for a change, somewhere.  And, with work and struggle, this could be exploited and built upon.  This would push the government further.  Which would expand the space for resistance, etc etc etc. 

Every victory - however partial - for the working class is to be chased and seized upon and celebrated (yes, critically celebrated, of course) because every victory for the working class, evey improvement in the position and confidence of the working class, strengthens the only force in the world that has the power, ultimately, to fundamentally change it for the better.

This isn't a fully worked out theoretical position.  There are plenty of better places you can go for that.