Fun but ultimately disappointing
Being the supposed final Fallout 3 DLC, Mothership Zeta obviously came with high expectations. Unfortunately for many, those lofty expectations probably won't be completely fulfilled. However, this is still a fun addon that will add several hours of gameplay as well as some nice alien loot for the player to enjoy.
Mothership Zeta takes place entirely aboard an alien spaceship, and like the previous DLCs is relatively combat focused with your PC having to mow down hoards of angry aliens. Fortunately, you can retrieve your gear early on and are also presented with an assortment of powerful alien weaponry as well (though they are not nearly as overpowered as you would think). The main quests are more or less linear and involve freeing prisoners and eventually, taking over the ship. Aside from the new weapons, setting, and alien enemies, there is also an additional gameplay feature which is presented at the very end of the DLC. I won't spoil it here but let's just say that there's a death ray involved.
On the down side, there is plenty of untapped potential here. The spaceship is filled with plenty of repetitive, abet good looking, environments and the DLC does not really take advantage of the advanced capabilities of the alien ship (and subsequent game play implications). Plus the aliens themselves are rather one-note and don't offer anything interesting story wise or character wise. They could just as well be mindless enemies as far as the player is concerned. Thus, if the major downside of Mothership Zeta is that none of the plot points (which are quite unspectacular) or characters (human or alien) stand out in any way. So unlike, for instance, Point Lookout, Mothership Zeta is quite soulless and significantly less entertaining,
Still, playing through the whole DLC and collecting all the captive tapes can take 4 to 5 hours, so there's certainly some fun here to be had. But by the end of the DLC, I didn't feel like I wanted to do any of it again. If this is indeed Bethesda's final Fallout 3 DLC, then it's unfortunate that it all ends on a whimper rather than a bang.