Updated to launcher 1.0.9 and average FPS dropped from 40 to 15. Research points to new launcher not recognizing/selecting appropriate video processor.
FPS drop caused the world I was playing to first "erase" entire chunks replacing them with a dark, inaccessible hole. Then generated so many sheep it crashed the game. Also when this world is played the launcher console will not close. Attached is the world save folder.
When I updated my game, I noticed a large fps drops as well, but once I backed up all my saves and then deleted everything in the .minecraft and redownloaded a fresh minecraft, it ran a lot faster. Try backing up important saves then deleting everything. I always back up my saves before updates anyway, so start doing that as well.