Well, if the corvettes are anything like these, they will be a game changer.
As far as the concept art, they are a radical departure from what we know.

This Advent ship look like a carry over from a 'Diplomacy' pact with the Vasari.

This Vasari vessel looks like a Manta Ray from from a demented Vasari to rage psychological hell on humans.

But this one, it has the smoothness of Advent ships, but that circular disk above. Floating shield, Frisbee of death. WTF!!!
It also have shades of a Vasari pact in ship design. All in all, Rebellion will be the must have RTS game for 2012. After getting and playing this game, only thing left is to sit back and wait for the world to end. Maybe??