Many note taking apps like Bamboo and Notability, Media apps like azul allow you to back up files and stream media from dropbox seamlessly. Most of these apps exclusively support Dropbox instead of iCloud which is a key advantage for choosing this cloud service. 18+GB free space is an excellent reason to try dropbox for you iOS, Android and Blackberry platforms today. You can download this universally supported, free iOS Appstore app from here. With the rise of cloud services from Microsoft and Google, it's very likely that dropbox will reduce it's prices in the long run.
Google And Microsoft: