I did not like the "new" look of Mail, so I'm very happy you can still use the "classic" look.
Many of the "changes" appear to be user interface issues, but others, such as enhanced security, go well beyond that and are worth further examination.
All of my key applications run without any problems, though not all of them support certain Lion features, such as the "full screen" view (this will probably come in time for most of the applications, and even if it does not, it is no big deal).
I do like the enhancements to Preview, which is underrated-it is much more than an "image viewing" application.
Apple OS X *is* the world's most advanced operating system, and this upgrade is well worth the price!
Review and commentary (c) 2011 by Patrick Jost
