The only area about which I was unsure was that Leela still believes in "intelligent design": I thought she had come to believe in science under the Doctor's tutelage? I suppose it could be that she's reacting against too much time with Time Lords... but this seems a little as though Cole is lapsing into writing "early Leela" rather than Leela as she has developed over her adventures; the discussions of evolution, drawn rather obviously from Richard Dawkins' The Blind Watchmaker, with Leela standing in as William Paley while Lalla Ward represents her husband, are the weakest on show here. On the other hand, they do the necessary legwork required in foreshadowing the Freaky Friday-type mind-swap that goes on in the story's second half: Romana suddenly acquires Leela's gift for primordial instinct, whilst Leela is all at once clinical and analytical (again, this is another nice nod to the idea of "becoming a different person" about which Leela is already concerned), though Jameson does a better job of selling the switch than Ward.
"You speak of your body like it is a machine, but it is not. How can such a big mind be so narrow?"
The Hallan/Melyin scenes are weaker than the rest of the material (especially the seduction stuff), but don't detract too much from the play's central strengths - and the pay-off at the story's end is rather satisfying, putting Hallan in his place and allowing Melyin to escape and start a new life, which is in keeping with the story's themes after all.
"There will be a place for you with me, for always, whatever face I wear."
"It is sad, the casting off of one life."/"And natural to embrace a new existence."/"Like the trees in autumn, burning off their coats of leaves, taking a new shape, but in time the green leaf grows back and the old shape can be seen again."
"People are alike everywhere. Even with one face they can show two."
"Luckily, this is more of a nuisance than a debacle."