What is "Ode on a Grecian Urn" all about?

In this excellent poem the speaker addresses a Grecian urn
which has two different scenes painted on it These scenes cause the speaker to consider
and meditate upon the nature of beauty and truth, and the way that this Grecian urn is a
symbol of eternal art and beauty. As the poem draws to its conclusion, the speaker
contemplates the significance of the urn for us as humans, saying that by meditating
upon the urn it "teases us out of thought," thought being that which makes us aware of
our own mortality and the cares of the world. However, contemplating the urn only does
this briefly, and we are left with an overwhelming sense of the ephemeral nature of man.
The Ode ends on a riddle as we are told that "Beauty is Truth, and Truth Beauty." Yet we
are left confused if the speaker is actually celebrating the beauty and truth that is in
the urn and that it symbolises, or whether the speaker is actually arguing that
contemplating the urn should make us more determined to make the most of our brief lives
and search for a truth that is beyond the cold remnant of a dead
civilisation.