After a truly exciting beginning and middle, the ending was rather disappointing.

I liked how Commander Zero listened to Lt. 90's suggestion of atomic particles, then said "The only reason I didn't mention it was because it's so...obvious." The ultra-patient Lieutenant lets this slide by, of course, just as he shrugs off the Commander later sneering at his suggestion, even though it was a quite reasonable one to make at the time.

Seeing an XL destroyed was quite startling. They never show the rest of the crew, although there presumably is one--Steve can't be the only XL pilot who flies with a crew. They did the same with the second XL ship. Not even a robot co-pilot. Were they trying to minimize the shock of seeing men die on the show?

How did Commander Zero and the Lieutenant become aware that it was an invasion force? The radios were knocked out, so Steve couldn't report seeing the missile launched from the cloud (he couldn't even report that he'd arrived), yet, when the cloud cover had reached the Earth's surface, the dialogue indicated that they knew something was in there, waiting.

Even before they were aware of the invasion, they knew that something was seriously off kilter. Why weren't the civilian inhabitants (such as Jonathan) sent away to a place of safety? Or at least make the effort? It would have been entirely expectable for Jonathan to sneak away from the rest of the civilians and come back to the tower to be with his father.

With the Commander bravely sounding off at the aliens, I expected the leader to at least shoot him in the arm, or give him a near miss. However, the Commander was apparently so shocked at seeing his son, he didn't even have a chance to tell him to run for it.

What the heck happened to Jonathan, anyway? Once his father made the call to Steve, and after he and Lt. 90 had been tied up, Jonathan just...vanished. He wasn't even there at the end.

The ending came straight out of "War of the Worlds". Just how did they get exposed to that disease, anyway? If it's as dangerous as Venus said, you'd think that the Earth inhabitants would have been inoculated long since, and the planet itself would probably be "clean." It would only have been slightly more plausible, but a lot more interesting, if they had shown Venus creating a culture of the disease from Zoonie's blood and somehow exposing the aliens to it.
As it was, having Steve & Co. saved from death at the very last moment because the aliens just happened to pass out was very anti-climatic. It was also rather silly that neither of them felt anything wrong until moments before they lost conciousness.

It was also utterly ridiculous for Commander Zero to try and claim that he had gotten the better of the aliens. After all, he and Lt. 90 had been securely tied up. Someone had to untie them, and that someone would know the truth. It was rather unkind for Venus to make her sarcastic jab at the "heros" (plural). Lt. 90 wasn't trying to claim credit for something he didn't do. His response simply indicated that he wasn't going to contradict his superior officer.

You'd think, that far in the future, that they would have improved the mechanics of inoculation to be less painful. Of course, you'd also think that an officer of the WSP would show a little more restraint. Lt. 90's scream was rather over the top.