The problem that appeared to be repaired in Safari 6 for Lion has reappeared in Safari 6 for Mountain Lion. I just installed it and went straight to my 25 "Open in Tabs" list of daily comics and there it was - the dreaded "Web pages are not responding" dialog.
That means that either what was fixed in Lion re-broke in Mountain Lion, or it was never fixed at all and I just didn't experience it during my brief test.
Also, two of my apps died in Mountain Lion: Little Snitch and Snapz Pro. Little Snitch has an update available, but Snapz Pro does not. Some of the features work but others were disabled to prevent a kernel panic (that multi-language overlay that appears telling you must restart your computer now).
More on ML next post.