The latest bit of information I received concerns your defenses.
Apparently, there is a chance that 70% of your defenses lost will be rebuilt. What ones are rebuilt is random, it could be shields, missiles, fighters, gauss cannons, etc. You could get lucky have have your big defenses rebuilt, or you could have all your puny little light lasers restored.
But either way, it is a good thing to keep in mind.
If you want some tips on building defenses, and a good defense strategy, then I suggest you click here.
UPDATE: Any defenses destroyed by Inter-planetary Missiles will NOT get a chance of being rebuilt.