"Canamar" is on the whole a pretty fun episode, although it's probably best recommended to fans who already like Enterprise, even though it's of no great importance to appreciating the overall series.
Apparently it was inspired by the later episode "Judgment," spun off from events that involved Archer becoming a prisoner of the Klingons (which itself served as a mini-arc at the end of the season). You should understand, however, that "Canamar" has nothing to do with "Judgment" otherwise, only the inspiration for the story, in which Archer and Trip find themselves prisoners of an alien culture. Come to think of it, there are plenty of episodes like this in other incarnations of Star Trek (another recurring theme in the writing room, I guess), although I stick by my assessment that you can probably get by on the minimal recommendation for the episode (that's what one out of three key elements listed at the top of every episode summary gets you, which in this ranking system is one out of four stars, and still means it's worth your attention).
The reason I rate "Canamar" for series rather than franchise is because, along with just about every other episode from the second season, it marks a clear progression in Archer's ability to make decisions for himself. As in elsewhere from the season, it's his ability to bluff that is again tested, and like in "The Communicator" Archer decides playing the bad guy is easier than being the good guy (which he is), especially since that image is more expedient to the face on the other side of the metaphorical poker table.
In this instance, he and Trip are onboard a transport ship filled with other individuals deemed to be criminals by an alien species. I guess this happens even when Starfleet is generally well-known, but it's easier for a ship in the Enterprise's circumstances (similar to Voyager's) for the uniform and reputation to mean nothing. The problems actually develop after Archer's innocence is cleared and he's free to go, because a mutiny breaks out and Archer then has to survive his own get-out-of-jail-free card, by aligning himself with the chief antagonist.
Now, it's true that Trip is also featured in this episode, but he's more the B-level protagonist. Archer gets the most interesting material, which is fine.
Now, all that being said, I wonder if it wouldn't have been more interesting as part of the Klingon arc at the end of the season. I know there are fans who prefer their Star Trek to be the traditional episodic material featured heavily in the original series and other incarnations, but I think it could have worked better if integrated back into the original source material. Still, I guess there's another episode that more or less covers the same material within that arc (we'll reach it soon enough). The choice is ultimately yours how much you take from "Canamar." See how accommodating I am?
franchise * series * essential * character
Memory Alpha summary.