Given that Kendra appeared in multiple episodes, I suppose she warrants a proper retrospective. But unlike Jenny Calendar, she only appeared in two stories, so it'll be a little less substantial. What I do have to say, you can read after the jump.
"You talk about slaying like it's a job. It's not. It's who you are."
Kendra, Buffy 2x10 - "What's My Line, Part 2"
While Kendra is a Slayer, and therefore a figure of great importance to the Buffy mythology, there really isn't that much that I can say about her. Her importance is obvious: her very existence flies in the face of the show's very premise. "One girl in all the world" and all of that.
Of course, the way in which she was called bespeaks a certain literalism in terms of the execution of supernatural edicts. We don't know much about the power that calls new Slayers, except that it apparently takes a strict constructionist view toward the "Slayer handbook:" Kendra is called upon Buffy's "death," even if it is a "death" that can be undone by a bit of untrained first aid.
But that's not really the point: the hows and whys of Kendra's calling as a Slayer are less important than the story it allows Joss and company to tell. Kendra existed to make a point about Buffy: to call into question everything she thought she knew about her calling as a slayer, and to offer her an easy way out. Of course, that's an option Buffy chooses not to take, and in fact it's Kendra's eventual death that leaves Buffy in a situation where her responsibility begins to become overwhelming.
Other than that, there's sadly not much else to say about Kendra. Probably what she'll be best remembered for is that awful accent. Apparently, the accent is actually a pretty accurate depiction of the accent used in a certain obscure region of Jamaica, but to the untrained ear it just sounds like a generic badly-done accent. Ah well.