It is not bad, but not good. This is the least liked DLC for Fallout 3, and probably from Bethesda themselves.
Why would I care to blast aliens in the face?
Aliens exploding; Space looks unique; Great beginning cinematic!
Why would we all agree that this is one of Bethesda's worst DLC's?
Short 5 hours; Boring; It's short 5 hours seem like forever since this add-on gives you painful headaches; Weapons are not that great!
So here you have. Mothership Zeta. What now? Get all the loot and run through the main quest's as possible to leave? Yes, as for Fallout 3: Mothership Zeta got a 6.5/10 for Fair.