It's inevitable: A new operating system is released, and something doesn't quite work like it used to on the prior version. Unfortunately, in the case of OS Lion, that something is Apple's own web browser. The problem is that almost a year later it still doesn't work...
For some reason, Safari has become a remarkably slow web browser in certain conditions.
Take, for example, this simple web page:
Opening that page and scrolling up and down using either a Magic Trackpad or a regular scroll-wheel-y mouse is a horrid affair in Safari (version 5.1.7, the latest official release at the time of this post). The page lags, stutters, and feels utterly disconnected from your scrolling. It's all very.... un-Apple like! The very same page in Google's Chrome browser scrolls up and down in quite the silky fashion.
A quick trip to Activity Monitor within OS Lion shows that Safari is pegging this nerd's CPU 100% when scrolling up and down here. Chrome? 15% CPU usage. This behavior has become quite commonplace while using Safari and for whatever reason, - Apple hasn't chosen to address the issue.
For reference, this test was repeated on a 2009 27" iMac (2.8Ghz quad-core i7, SSD, 16GB RAM), a 2011 MacBook Air (Core i5 1.7Ghz, SSD, 4GB RAM), and a second 2011 MacBook Air (Core i7 1.8Ghz, SSD, 4GB RAM).
I'm not holding my breath for an OS Lion fix for Safari, but hopefully Mountain Lion will finally devour the issue.
*UPDATE* - August 7th, 2012
Hey, guess what? The new Safari 6.0 present in OS Mountain Lion completely solves the above issue. Well played, Apple. Well played indeed...