iGetter will automatically resume downloads when possible (some sites prevent this). This means that you can put your Mac to sleep half way through a download, and when you turn your Mac back on it will resume where it left off instead of going back to the start.

You can pay $20 for an iGetter license to help the developers, but it won't unlock any additional features - all of the pro features are available in the free version.

Downloading stuff while you are on your computer can tax the internet connection. With iGetter, you can schedule downloads for the wee hours of the morning when you (probably) aren't using your Mac.

This can also help with data-caps, as some providers have unlimited times early in the morning during off-peak times.