I've used Logos throughout my years of seminary and believe it is one of the best programs out there for Bible study and research. Logos is one of the most comprehensive and powerful software packages on the market - now having recently added a iPhone/iPod app.
Although this software is top drawer...it does come with a hefty price tag.
But during Christmas they are running a 25% discount code: DECKTHEHALLS
If you were thinking of purchasing Logos Bible Software, make sure to take advantage of this discount!