Have I seen a different scene? I thought that he spent most of the fight on the ground. :)

: The strange woman (I can't recall her name)....

Catherine.

: Back at the river, Marge has goaded Challenger and Malone into following her into the jungle to search for the gateway, when they suddenly stumble onto...the same set they used in last week's episode when Challenger put the giant bowling ball into the pocket and became All-Powerful-Challenger.

You're right. It was the set they used for the ruins of Atlantis in "Absolute Power". However, one can't really blame budget-minded producers for recycling that set.

: Leaving Veronica to take care of the other two, Roxton continues on into the jungle as Ned calls out "Watch out for Kemper!". I guess that somehow, Roxton knows who Kemper is, even though he's never met the guy before!

In the German translation they turned the line into "Watch out for a man....", thus saving themselves any need for an explanation.

: A couple of good things about this episode is that the plot is much better than any of the previous ones. I see a very strong improvement in the script.

This was certainly one of the best scripts they've had so far.

: I also noticed that Malone is becoming more capable, and Marge has developed an Indiana Jones quality as well...

That's just the Harrison Ford hat she's wearing. :)
You're right, there's a tendency to make Marguerite more capable in that respect. Malone also, but slowly.

: In this episode, we learn that Malone has shown Veronica how to shoot a gun "once or twice" and that she can also work the balloon, a skill that Malone possesses.

What I found more interesting, was Veronica's reaction of disappointment when she learned that Malone didn't come back to her. For all Veronica/Malone relationship advocates, here's some hope.

: I've also noticed an improvement in Will Snow's acting, and Jennifer O'Dell seems more comfortable with her character. The others seem to work together a little better now, too.

I really didn't notice any significant change in the acting. It was just that they could work from a better script this time.

: This would've been one of the best episodes of the series except for the two glaring mistakes: (a) the failure to believably secure Roxton, Veronica, and Summerlee to the chairs,

Remember also the hardly confining cage in last week's "Unnatural Selection"

: and (b) Ned's warning to look out for Kemper made no sense.

As I said, no problem for us watching over here.

: There was also a failure to give us some cheesecake in this episode...

Huge drawback. :)
All in all, still one of the top three episodes of the season so far. I liked the fact that they raised the emotional content in this episode to a higher level than they normally seem comfortable to do.