I think one of the good uses of enjambment across stanzas is to convey sudden movement, as Larkin does with the horse slipping its lead, Wilbur with the sudden darting of the trout, or as Dickinson does with the sudden movement of the snake:
A narrow fellow in the grass
Occasionally rides;
You may have met him,--did you not,
His notice sudden is.
The grass divides as with a comb,
A spotted shaft is seen;
And then it closes at your feet
And opens further on.
He likes a boggy acre,
A floor too cool for corn.
Yet when a child, and barefoot,
I more than once at morn,
Have passed, I thought, a whip-lash
Unbraiding in the sun,--
When, stooping to secure it,
It wrinkled, and was gone.
Several of nature's people
I know, and they know me;
I feel for them a transport
Of cordiality;
But never met this fellow,
Attended or alone,
Without a tighter breathing,
And zero at the bone.
Dickinson's enjambment isn't as extreme as Larkin's or Wilbur's, but while all of the stanzas save S3 end in a very natural end stop, the larger thought of S3-S4 needs basically two connected rooms, as Katy pointed out, and running the sentence across the stanza break gives it a "whip-lash" as Dickinson mentions next, the movement of of a snake suddenly darting.
My general thought is to keep all the stanzas as separate rooms unless you have a good reason to kick out a wall. Larkin, Wilbur and Dickinson all had good reasons, and it adds to the poems. However, randomly arranging text until it looks aesthetically pleasing until you actually try to read it is one of the classic evils of typesetting. I have a friend who's regular prose article was printed by the magazine designer in a five by five grid of twenty-five separate text boxes--visually, the page looked gorgeous; actually trying to read the text was a nightmare.
If doing something like that will ruin prose, it will certainly ruin poetry. Besides which, there are already some tried and true typesetting conventions that can add a little visual interest to a poem without detracting from its readablity. One of the oldest is simply chaining stanzas down a page, like this:
A narrow fellow in the grass
Occasionally rides;
You may have met him,--did you not,
His notice sudden is.
The grass divides as with a comb,
A spotted shaft is seen;
And then it closes at your feet
And opens further on.
He likes a boggy acre,
A floor too cool for corn.
Yet when a child, and barefoot,
I more than once at morn,
Have passed, I thought, a whip-lash
Unbraiding in the sun,--
When, stooping to secure it,
It wrinkled, and was gone.
Several of nature's people
I know, and they know me;
I feel for them a transport
Of cordiality;
But never met this fellow,
Attended or alone,
Without a tighter breathing,
And zero at the bone.
Another, which I noted going through my copy of The Ingoldsby legends, is to split any lines with Leonine rimes in the middle of a long narrative into two lines, the first indented one tab, the next two, so there's a little extra bounce to emphasize the rimes, as well as a visually pleasing break in a long passage of text. I'm not certain if that was the poet's idea or the publisher's, but it reads just about the same and certainly does look prettier.
[This message has been edited by Kevin Andrew Murphy (edited March 13, 2005).]