ChessBase is releasing new products all the time, and one worthy of consideration is the 2012 edition of their premier product, the Mega database. The latest edition includes 5.1 million games, 66,000 with commentary, which makes it an excellent value when you compare it with the number of games and annotated games in a book. You'll find many opening surveys included and opening analysis of recent games (the database is up-to-date through mid-November of 2011, and there are 782 annotated games from the first ten and a half months of this year alone), so it can be used at the very least to supplement one's opening materials in a thoroughgoing way. There are also various keys for the opening, middlegame and ending, so you can easily research openings from scratch, or do a search for games with noteworthy attacks or combinations, etc. If you're a reasonably serious tournament player and don't have it, I'd heartily recommend it. Those of you with previous editions will have less motivation, especially if you've been keeping it up to date with TWIC or especially ChessBase Magazine, but they have some more affordable upgrade offers you might consider.
For more info about the product in general, and to buy it in disc or download, go here. To buy an upgrade from Mega 2011 (disc or download), this is the link. Upgrading from Big 2011? Go here. Finally, if you'd like to upgrade from an a pre-2011 version of Mega, then this is the link for you.