Hi Cap'n Refsmmat, fascinating work.
You mention some issues with rhythm. Check out the publications of Kevin Knight at ISI, he had papers at ACL this year and last about computationally detecting rhythm in poetry, though last I heard he had the same difficulties you describe with context and single-syllable words. Also try to find Charles Hartman's book "Virtual Muse", which discusses the meter-analyzing poem Scandroid (which is available on the web, its documentation also describes the algorithm it uses) I think he addresses the second question quoted above. If you really want to get into automated metrical markup, there's a pretty good bibliography out there, too.
You may be interested in some of the other n-gram poetry generators out there, check out the guide to interactive poetry generation systems I wrote on netpoetic.com.
If you're still using word 4-grams, I think the corpus size requirements will constrain you. Personally I think trying to remove the human from the creative process is ultimately impossible (after all, a human wrote the program and sets the parameters...) so I embrace interactivity. Take a look at the group blog Gnoetry Daily, we use interactive and unsupervised word and character n-gram generators, stochastic beam search with phonemic evaluations, rule-based generators, word-substitution techniques, and similar approaches to generate poems.
