I updated Minecraft to 1.7.4, so that I can seize the twitch integration. I installed it, and logged out to play another day. When I came back, the launcher didn't recognize the fact that my computer had already installed 1.7.4, and still said "Ready to download & play 1.7.4." There is no affect on game play, but this should not happen.
Duplicate of MCL-1516 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.