I can't find a way to update the affected versions for this bug, so I'm stating it in a comment instead: bug is still present in Minecraft 14w10c.
Side note: The bug will not magically fix itself. Mojang needs to remove the hardcoded disabling of IPv6. To keep asking if the "bug is still present" is pretty useless.
I can't seem to find a way to confirm or append to this issue, but I came upon this bug myself now, as I was testing to set up an IPv6 only server. Issue is still present at 1.6.2 under both Linux and Windows 7.
I personally don't understand how Mojang can blame "broken IPv6 stacks" on connection issues, a broken IPv6 stack would for instance render Google and Facebook unusable for affected users.
This bug is very much still present in the current version, and I've observed the same problem in chests, when you hold down shift and quickly click on different items in the chest, only about a third of the mouse clicks are registered, so two thirds of the items you clicked will remain in the chest you're trying to empty. This severely breaks the immersion, and I can't really see myself playing this game until the UI is usable.