I would definitely not recommend using individual <svg> nodes. Instead what I did was wrote some basic wrapper functions to decompose and re-compose the internal attributes of <path>. If you get a chance to read the spec you'll see that you get the option of assigning RELATIVE or ABSOLUTE coordinates, which makes it very easy to do a simple editor like what you've done within a single <svg> node.
I found that (for my purposes) working directly with the objects was a huge win in terms of performance.
It's not the "be all end all" solution, but helped my project enough to where performance issues were no longer noticeable.
It also seems that, depending on the browser, they have dug themselves in the same hole as before. Moving the polygon or one of its nodes around triggers a layout in at least Chrome and IE, exactly what they wrote were trying to get rid of. Maybe the demo does not yet show their new implementation; I saw way too many SVG elements, but no CSS transform on them.
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