I'm gonna give it a B+/B.
Many others have sung Billingsley's praises more eloquently than I can; he doubtless made the show. (I have give Blalock a nod for her solid back-up work as well; after this and "Stigma", I enjoy how Phlox and T'Pol's characters play off each other, especially in serious debates that involve both objective rationale and deeply personal emotions. It's not an arguing, give-and-take dynamic, but a supportive and sympathetic yet coolly intelligent meeting of colleagues who're a bit more experienced than others on board.) And I actually sort of liked the spelunking scenes; as someone who was thoroughly sick of all the "Trapped in a Confined Space!" episodes last season, I enjoyed a set - a cave set, the most overused of all! - which actually seemed original and convincing, and I found the cool-yet-intense blue-wash here both visually pleasing and a nice break for the eyes from Enterprise's usual steel-grey palette.
The episode was slightly soured, though, by viewing it in light of recent events. We get, in quick succession, the "I'm going to help you whether you like it or not" pronouncement by Phlox, the "believe me, you don't want to get in a war with us" showdown with Archer and the Xemians, and Trip's "we'll SHOOT you if we have to" threat to the geeky, out-of-touch, effete scientists they're supposed to be rescuing.
Now, Archer's tough "honor your part of the bargain and we'll honor ours" fiat was the best way to deal with the Xemians, I unequivocally grant. I'm a bit shakier on Phlox's words, but perhaps he figured that the only way he was going to get the guy to believe his goodwill was to force it on him (and perhaps he didn't really *mean* it, but was just using the tack as an opening for his big speech). And, now, I can completely understand Trip's feelings upon hearing the Denobulans' initial refusal, having been through a perilous and physically exhausting climb, having almost died, and having had a good friend seriously injured on the way (good *God*, that was a horrible accident for Travis, having his leg *jammed* like that). Having his whole persuasive argument to the Denobulans be "We went through hell to get to you, so we get to say what you do!!" makes me a bit uneasy, however, particularly since the show seems to agree with his viewpoint - stacking the deck character-wise pitting Rough Hardy Guys against, as I said, rather effete, out-of-touch eggheads (their climbing abilities notwithstanding), having Trip threaten to shoot them *again* on subsequent occasions, and failing to having either Trip *or* Reed offer a single other persuasive argument to the Denobulans, not even a brusque "hey, we're not the Denobulan Science Directorate, and we're under their orders - like you are. You got a problem, you take it up with them". Again, I understand the exasperating nature of the situation, but if Trip can't hold together in that manner under pressure, I have to question how he's risen so far in rank in the first place. Anyhow, the whole situation just left a bad taste in my mouth. (Recognizing a bit of a physical similarity between Trip and George W. Bush didn't help.)
Now, the heroes' actions in each of the three scenarios can be counted as varying degrees of defensible, but taken so closely together, the ep seems to be tinged with the argument that humanity (and its associates) has the right to impose what it wants on members of other societies and cultures, relying on force and advantage to enforce its moral will. That's distasteful without the debatable real-life parallels.
To repeat an old complaint - humanity should go out in space and have its perceptions challenged, and it's instead having them relentlessly reaffirmed. I have no doubts, from both a looking-at-it that humanity has something great and wonderful to offer the galactic community, but it should be *learning*, too. I liked this ep all right, but I wish it could've broken out of the box a bit more.