I've implemented the horizontal "getaway" style drop-down menu on our soon-to-be released site. In testing, Chrome 1.0 and Safari 3.2 for Mac push the layout away from the drop-down zone, appearing to break the layout below the menu.
See the screenshot of Chrome 1 in XP:
http://pandora.cii.wwu.edu/test/images/chrome1xp.png
However, I just checked Browsershots.org and for both browsers the next versions coming (Chrome 2 and Safari 4) both seem to fix the problem. I think we're not going to fret about this for now, knowing (hoping) that coming versions will fix it. Just thought I'd post my findings.
jb