I've been using the Android version of the Gospel Library for about a month now and I really like it. I haven't used it heavily, but when I don't have my scriptures with me it's a quick way to look something up or read along with the lesson in Elders Quorum. If you've got a mobile device that is supported you should give it a whirl.
New Mobile Apps Available - With the combined resources of the Gospel Library and the Mormon Channel radio station, you can study or listen to the scriptures and other Church publications anytime on your BlackBerry, iPhone, Android, or Palm. Learn more at our mobile apps page. [LDS.org Home Page]