Not an awesome post but for any interested in the AnimatedCluster strategy I have updated the demo site to work properly with OpenLayers 2.12.
In version 2.12 symbolizer are richest than in 2.11 and required to set the labelOutlineWidth
property to some low value to show the labels fine:
var lowRule = new OpenLayers.Rule({ filter: new OpenLayers.Filter.Comparison({ type: OpenLayers.Filter.Comparison.LESS_THAN, property: "count", value: 15 }), symbolizer: { fillColor: colors.low, fillOpacity: 0.9, strokeColor: colors.low, strokeOpacity: 0.5, strokeWidth: 12, pointRadius: 10, label: "${count}", labelOutlineWidth: 1, fontColor: "#ffffff", fontOpacity: 0.8, fontSize: "12px" } });