All three follows most of defined standards, while Trident (IE ergo Microsoft) has always tried to set their own standard. In past (only eight years ago) when IE stood for ~90% of market share, it was worth thinking about it. But now with the share dropped to ~30% (and falling), I don't know if it still holds true, specially with the newer versions (IE9 and IE10) talking up the older territories. These newer version of IE have better complacency with the given standards.
To the point, just read on nettuts+, jQuery is going to drop the support for the older IEs', in a elegant way. Maybe it is time to get in the train, and do it.
It has been a while since I decided to drop support for any IE < IE8, and I think this is just going in the right direction.It has been a pain to get some of the thing to work in older IE versions, even IE8. Now I think I am going to update that policy to nothing will be coded by me, for any IE < IE9. With one exception, can't really implement this in my professional life, have to do what the customer asks for.