Unlike the Mac, Windows lets applications install files all over the system and program folders. The result of Windows allowing apps to install files or DLLS in many locations is it can wreck havoc with operating system stability. Apple has a better approach.
OS X confines application files to the application, system's library, and user's library folders. Some application preferences are system wide and others are specific to a certain user (which is why there are two library folders), but hints in OS X Lion suggest things are about to change.
One of the advantages of having an iPhone or iPad is to stay connected while away from the computer. Out of the box, the iPhone comes with email, calendar, and a web browser to help. There are many more ways to make the iPhone or iPad more valuable. Here are some essential iOS applications that can be used to stay in touch while out and about. All of these have both an iPhone version and an iPad version.
Staying connected means having your files wherever you go. Apple does not provide a solution yet, but Dropbox does. It will sync seamlessly in the background to all of your computers. When you are away from a computer, the app allows access to all the files in the Dropbox folder on any device. A good example of a use for this is to bring along a hiking map in Dropbox, instead of toting the whole hiking book along on the trip. Dropbox does come with disadvantages, since it is not a full featured file browser like Finder. Many of the standard Finder tools like "rename", and "file move" have not been added. Even with these issues, Dropbox is still the only solution giving you access to your files on the computer anytime, anywhere. Dropbox is free with a 2GB storage limit.