I use the Leef iBridge 16GB for one thing – to watch magic trick instructional videos on my iPhone.
Have you noticed how horrible the iTunes app has become? Apple has lost the plot on this confusing piece of bloatware and I avoid it as much as possible. I buy a lot of card trick videos from Penguin Magic, and instead of trying to get them onto my iPhone using iTunes, I just stick the USB end of the Leef iBridge into my desktop computer, and it shows up as a USB drive. I drag the movie files onto it. Then I unplug it and stick the iPhone end of the Leef into my phone, open the Leef app, and there are my card trick movies. It's foolproof.
The Leef also makes it easy to copy photos from your phone to the Leef, so you can copy them to your computer without using iPhoto (another horrible app).