The Rolls Royce of Bible Software. It's costs more, but it's worth more. I've been using Logos Bible Software as my primary study tool for several years. It has everything I need and more to do effective Bible Studies. If your a Pastor, Bible College, or Seminary Student this is a must. There is a learning curve, but it's well worth the time.
I consider this the best free Bible Study Software available. Even when using Logos Bible Software, I keep e-sword running on a separate window to do quick searches, check additional commentaries, look at maps, evaluate other translations, etc. Additional downloads such as Illustrations, books, etc are often at a fraction of the cost that you'd pay at Logos. I've often used E-Sword's software, especially the maps on overhead for teaching classes. It's easy to use and fast. Since it is free, I'd suggest giving a donation to help e-sword continue providing the valuable service.