I really love the Endnote Ipad app. It makes me so mobile with my research which is really important as a working mother. Now I have everything I need without carrying around piles of paper. Its perfect for working from the car while waiting for children at ballet or soccer, its perfect for reading while travelling, its perfect for meetings when I need to point people to a particular reference.
Basically I have Endnote on my computer with all my references in it linked as pdfs. This syncs to the cloud with Endnote sync. The Endnote app syncs with the cloud too, which means I can access my references, including the pdfs from my ipad. You can predownload the pdfs you want to read so you can access them even when you are not connected to the internet (like on a plane).
Like all apps it does not have all the features of the full programme, but it does have a good search function, does allow you to see groups you have created and does allow you to annotate documents. But used as an extension of the computer version, rather than a replacement, its perfect.
Check it out here https://itunes.apple.com/nz/app/endnote-for-ipad/id593994211?mt=8