The contenteditable attribute is not part of any standard and is a MS add-on / "enhancement" / proprietary hack, so beware of browser incompatibility. From a standards promotion point of view, i'd strongly recommend NOT using it.
did some searching on W3C, and this i didn't want to hold back:
Answering the question if there were "any other cool features", Etan Wexler replied:
Speaking of the Web in general, the putative coolness of a feature is inversely propertional to the utility of the feature. I will leave it at that.
The rest of the polemic on the attribute can be found here