This is an old post from 2012. As such, it might not be relevant anymore.
Seems as though the jQuery team are planning on dropping support for IE 6/7/8 in jQuery 2.0, expected to be released in early 2013. Now, although I don’t particularly like IE, I think that might be a little too aggressive a development path. Unfortunately few people still use IE 6, a little more 7, and quite a chunk 8.