Aiseesoft iPhone 4 to Mac Transfer is an iPhone management tool. It allows you to copy content from your iPhone 4 to your Mac. There are two versions of this app: Standard and Ultimate. They are identical, but the Ultimate version lets you backup different types of content. For example, with the Standard version, you can't backup photos, your camera roll or SMSs. That is why I downloaded and tested the Ultimate version.
Upon launching the application, you will see your connected devices listed on the left part of the screen. If you expand them, you will see all the data that you can backup, including music, movies, TV shows, podcasts, etc. You backup your entire SMS history and your contacts. There is also support for your photos and camera roll. One bit of bad news is that if you have updated to iOS 5, some of this app's features won't work. For example, I couldn't get the app to find my photos on my iPhone. A future update to the application will surely fix this, though.
In short, this is a very complete app to download your iPhone's content to your Mac, but you can't use it to put content on it, and some "management" apps let you do just that as well.