Thanks to the Mac App Store, users can now download their purchased applications and download them on any machine they are using. As a result, it is possible to turn this into a portable computing platform by logging into your Mac App Store account when you are using someone else’s system.
To do this just open the Mac App and click on the Store menu item. If the person who owns the machine is signed in, just click Sign Out. Then re-click the Sign In item from the Store menu and enter your user name/password. Now you can download any software you need to use, upload any content you create to a cloud service like your Mobile Me iDisk or a DropBox account. Alternatively you could just move it to a USB flash drive. To be legal and safe be sure to uninstall any of the software you downloaded and then sign out of your Mac App Store account so the owner doesn’t download software with your account.
There are some limitations. First, you have to go through the pain of downloading and setting up apps. This can take time especially if you are at Grandma’s house and she’s still on dial-up. Another problem is that your own user settings won’t be available for the software. So this would only be practical if you were planning to work on the guest system for a long time – like a week-long vacation at a friend or family member’s house or if you are doing mission critical work and must have the software that is not already on the machine.