The whole episode is concentrated on out three favourite Ferengi and yes, Nog and Rom finally get some well deserved screen time. The subplot is practically non-existent and that’s even good.
For me, the whole episode is a parody of the movies and TV series portraying good aliens thought to be evil Martians coming to take over. We’ve got the trigger-happy Bad Military Guys, that are convinced that our ‘visitors’ came to conquer the planet, we’ve got an open minded scientist and a tender, loving nurse who, of course, if the scientist’s girl.
If you start to take it seriously, well… the plot holes have the size of a watermelon and if it was a regular DS9 episode, it would make it unwatchable but here? Why not! All for the fun! Won’t describe all the cliché gags used here but they are actually funny. Sure, there is some drama but it fits greatly into the plot and, on contrary to some other episodes, doesn’t try to ‘take over’ (like the evil aliens would)
This is a fine example that, while DS9 is the darkest of the whole Star Trek spin-offs, it’s also capable of creating episodes that are pure fun.