Quote from DastardlyDarwin
Just out of curiosity, are there any plans to remove (or edit the text to your liking) the 1.5 client's nag message about 1.6 being available? I don't know how labor-intensive that would be, so I may actually be better off meddling with my firewall settings to block the URL it checks.
From changelog for BTW version 4.86 (july 6/2013)
"-Removed Mojang's update pester from the title screen, given BTW is not yet available for 1.6, and given that it was frigging annoying "