uh... for just the poem alone, I was going to go with the speaker being Spike, because he's always the one loudly proclaiming his eternal love.

Quite right.

In the context of the play as a whoole... I've got no idea. I don't actually think you can relate either character to Hamlet himself very well. Maybe another shakespeare character[s] instead?

Yeah, I agree that Hamlet in general doesn't work for Spuffy - I just like questions like that. I can't really think of a Shakespeare play that does work, but now I want to play, so I'll muse on it some more. The Gunn/Fred/Wesley Othello parallel from AtS a couple weeks ago was obvious, but still enjoyable. Connections are yummy.