In some openings theory changes rapidly and the books covering it soon becomes obsolete, at least when it comes to the "hot" variations. 10 years ago, the Sveshnikov was seldom played at top level. (At least that's my impression from reading the list of  variations played in the tournament which lead to the "Sicilian Love" book.)  A well written "old" book can still be very useful for the general understanding of an opening. I haven't read Sveshinkov's own book from 1989, but I've been told it's still an excellent read.

The QGD hasn't changed very much. It's only the Bf4 line that seems evolve. 

You can do updates of the theory yourself with new games from TWIC or other sources, but it's very helpful with books that do that. Really good books also include plenty of original analysis, something which saves the reader a lot of work.

I recently received Dautov but truth be told he is already outdated in main lines If you are a black player playing the main lines (either c5, or Nbd7) then you may not have the latest theory.  New in chess yearbooks and Ruslan's site here is good for that. you might also want to consider the kasparov DVD which contains a nice summary of latest ideas in 5. Bf4.

But of course the best way to study an opening is to go through as many annotated games as possible. So you might want to get the Dautov CD anyway. Furthermore the nature of QGD is such that evaluations don't change very much so latest theory is not so important. 

And if you are looking for coverage on sidelines e.g. (6...a6, 6... b6 etc) Dautov is still unbeatable. 

Overall I give it 6/10, but this is only because I already have pretty much material on 5. Bf4 from the aforementioned sources.

You sound like you really need Khalifman's Opening for White According to Kramnik. The "relevant" volume is 5. However it is from White's point of view and there is nothing about the Bf4 system. Khalifman recommends Bg5. If you have questions, E-mail me.

The relevant volume of Khalifman's Opening for White According to Kramnik should cover all these lines.

So sadler is a must for qgd. Are there other good books/cds? Lalic's book on Bg5 lines came out about the same time. Is the theory still of any good?

On QGD exchange: i read a couple of good reviews of heinrich's new cd. Any other opinions?

On 5. Bf4: How do you think colin crouch's old 5. Bf4 book is holding up to current theory? Is dautov's cd complete is its coverage and is it any good now?