I'm still reading through T.S. Eliot's anthology of poetry, despite the fact that I've already graduated and am finished with the readings I was assigned in that book. It's the sort of poetry that catches hold of you and won't let you ignore it for some time. I leave the book each time with a profound respect for Eliot's poetic mastery, then come back and realize how meanly I've shortchanged his accomplishments.
One thing that strikes me each time I read one of his poems is the incredible economy of language. He never puts in a word that adds nothing to the meaning. Rather, the poems consist of the meaning itself, pared down to the most essential language. All really good poetry that I've read seems to be like this, actually. I don't pretend to be at all knowledgeable on the subject - I neglected poetry (except for that of Lewis Carroll and Edward Lear) dreadfully until I read the "Raven" two years ago. But it seems to me that this brevity packed with meaning is the essence of good poetry. The varying structures, clever or original use of language, etc, are all only useful when they add something to the meaning of the poem. They're simply tools for the poet to use in order to pare all superfluity out of his ideas.
It is funny that the most common depiction of a poet I've ever found in movies and books (a prose writer must be much different from a poet, I think) is of a rather muddle-headed, overly sentimental person, whose head is floating randomly through the clouds. But if you think about it, a really good poet must be more clear headed and practical than all the rest of us. He or she should be able to see through common phrases and ways of thinking to get at the very root of things, and to express them without writing a thousand-page philosophical tome.
The only really frivolous type of poetry is bad poetry. Bad poetry is poetry in which the poet is laconic because that happens to be the fashion, or flowery because he or she is really more of a lover of language than a poet, per se. It also has something to do with the poet's ability to express himself accurately, of course. The first problem I mentioned in this paragraph has to do with lack of a poet's mind. This one has to do with lack of a poet's craft. If you have brilliant insights into the human condition, but can't use language well enough to express meaning with really poetic brevity and facility, you may have the mind of a poet, but you'll have to settle for being a philosopher.