The ticket's status is in "Needs Discussion", they are still working on this and the only way you can use this feature would be to install the patch. However, reading the last post you can see there are still bugs in it and they are "working on it". (in quotes because it's a minor priority and you could be waiting for a while.)
Alternatively, depending on the length of the content you put in there, you might be able to use a background graphic like such:

strokeColor: "#00FF00",
strokeOpacity: 0.7,
strokeWidth: 3,
fillColor: "#FF5500",
fillOpacity: 0.7,
pointRadius: 12,
pointerEvents: "visiblePainted",
//Supported values include “circle”, “square”, “star”, “x”, “cross”, and “triangle”.
graphicName: "circle",
label: "${order}",
fontColor: "#000000",
fontSize: "16px",
fontFamily: "Courier New, monospace",
fontWeight: "bold",
//Valid values for horizontal alignment: “l”=left, “c”=center, “r”=right.
//Valid values for vertical alignment: “t”=top, “m”=middle, “b”=bottom.
//Example values: “lt”, “cm”, “rb”
labelAlign: "cm",
labelXOffset: "0",
labelYOffset: "0"