Around the office Lion is loved and, well, not-so-loved depending who’s asked. Some features like Natural Scrolling are pretty universally hated, and luckily that feature can be disabled. A better-received feature is Resume. With Resume , you can quit an app, and come back to it later with all windows right where you left them. If you have many Safari windows and limited memory available, you can now quit Safari to free up memory, and re-launch as needed without having to navigate to pages you know you need to view.
Sometimes, though, you’ll have a bunch of windows open but want an App to re-open without all the windows from the last session. Just hold down Option while selecting Quit from the file menu. Quit will change to Quit and Discard Windows.
Lion adds the ability to sign PDFs in Preview. This is immensely useful for me as I often need to sign documents, scan them back in, and email back to the sender. Now, just open Preview, go to Preferences -> Signatures and you can then hold up your signature in front of the iSight or Facetime camera built in to your Mac. This done, you can sign a PDF by selecting the Signatures option under the Annotations toolbar.
Another very useful feature is Sandboxing. It’s transparent to the end user, but it also provides robust protection from malware. Basically each application and each website must run in its own Sandbox, with limited access to system resources. Before, should a compromised application be run with administrator access, it was much easier and more likely for that application to gain access to sensitive information and system resources.
Sandboxing is a big deal. While MacOS X has been largely unaffected by malware, this preemptive step will help keep that record going far into the future. Ars Technica has an excellent article that explains Sandboxing in greater detail.