I have not upgraded ML as I am waiting for my redemption code but did update one machine to Safari 6. Instantly it broke my compatibility with Flash. I have been running 10.3.183.7 and putting off installing Flash 11.x because in my experience 11 has had numerous issues. I won't run it anywhere. 10.3 was much more stable. Safari 6 requires Flash 11 apparently because all Flash content/plug in is blocked and it tells me to update before I can use Flash. Hopefully it works better with Safari 6 than it did with 5.x.