The first thing I noticed about this poem was the distinct rhyme scheme (aabbccdd,etc.) coupled with the strange way the lines were broken up with a ridiculous number of dashes. It all flowed very nicely in the end, I just thought the pauses were slightly awkward.
Then there was the disheartening beginning to the poem, "From childhood's hour I have not been as others were." Which is followed by more descriptions of how the speaker could not relate to others, or love the same things others did. The turning point in this poem is the italicized "Then" at the beginning of the ninth line. This turning point also happened during the speakers childhood, apparently. Poe repeats the word "From" to start off the next six phrases, which are describing natural elements from which this "mystery which binds [him] still," is being extracted. We are never actually told what this mystery is, so we are left to infer from the context that it came from some sort of celestial power, or something to that affect, and that it completely altered the course of his foreign, misunderstood existence.
The last few lines stood out to me though, and I don't entirely understand why Poe structured them to do so. "And the cloud that took the form (when the rest of heaven was blue) of a demon in my view." This is the only spot where Poe chose to place parenthesis, which makes the line stick out in the way it both sounds and looks. I also thought it was interesting how he chose to interject the idea of the heavens, when he could have just used the word sky, in the middle of the description of a demon-shaped cloud. I assumed he was referencing some biblical aspect of his loneliness, but I could be wrong. Other than that, I thought this poem could have been summed up in about three lines, and, as nicely as it flows, I found it very unremarkable.
PS: I commented on Becky's post on Sort of a Song, and Mandee's post on Desert Places.