<blockquote>
<p>One concern is that I think it only has SVG and Canvas renderers, which presumably means no vector overlays in IE before version 9 which may be a bit of a problem.</p>
</blockquote>

<p>No, <a href="https://github.com/CloudMade/Leaflet/blob/master/src/layer/vector/Path.VML.js">there's a VML renderer</a></p>

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