Long ago that was my defense against d4. White's lines are much better now. A draw seems to be the most probable outcome.

Against the Gruenfeld I tend to go for 4.cxd5 Nxd5 5.e4, gaining a classical pawn centre.

Well, the classical pawn centre can be an easy target for Black. That's what makes that line more dangerous if you're not sure about what you're doing.

Fatcat, it would help if you read up on hypermodern principles. Centers can be undermined.

Yes. Black encourages White to occupy the centre so that he can harrass it. I occasionally essay the Grunfeld myself but haven't found it an easy opening to play as Black. As White, I still tend to adopt the line I learnt as a child from Harry Golombek's Instructions to Young Chessplayers, which is that advocated by fatcat2. It is no longer fashionable but at least I can remember it! I think a more cautious approach by White is likely to be more productive in the long run.

Black branches into a sort of Slav setup.

This is considered fairly equal and drawish.

Not the best move. If you prepare a piece to be flanchetto'd you should always if possible do it right away as it becomes a weakness for white gains attacking advantage because if the piece isnt developed right away black has to waste time and losing an advantage to develop it.

I would play 7...dxc4 8 Bxc4 Nd5.

Black is behind in development, and is wise to hurry ahead with it.

Though 7...dxc4 8.Bxc4 would represent a small gain in time for Black.

...Re8?! builds toward an e5 pawn break.

maybe bc4 with the idea if white plays be2 black has Ne4 which is aggressive as if white chooses to take the knight he is met by d takes e4 attacking the pinned piece also if white refuses black has Nxc3 bxc3 and Qa5 coming

Judging by the rest of your comment, you mean 7... Bg4. I would not have responded with Be2, losing tempo, but 8. h3, forcing Black to abandon the pin or else exchange at once. (8... Bh5? 9. g4!)

I'm not convinced 0-0 is best. I would consider h3 first. Blacks LSB has little scope, and ...Nh4 is met by Bh2.

Um, what is doubled pawns again?

Doubled pawns are two pawns on the same file. Like my f-pawns would be after 9... Nxf4 10. exf4. They can be a weakness, because they are unable to defend each other and the front one cannot be defended from behind.

Here Black needs to play f6 anyway to break with e5. I would try Bh4.

How?

Though Black's centre is in fact quite well supported by his pieces.

If Black's aim was to double White's pawns, it seems inconsistent to immediately offer him the chance to undouble them. It might have been better to look for a longer term strategic advantage by leaving White with an awkward structure and developing first but ionadowman is right and the Bg7 needs lines opening for it to flourish.

black is the kind of player id love to play against, i welcome this trade of pawns

Very exposed. Perhaps now Bxg6...

No, I don't take that sort of risk in a tournament game. If the bishop goes, only the queen is able to reach the kingside quickly, and one piece isn't an attack.

Nuntar is right.

Yes. As I've learned to my cost, attacks have to be properly prepared. Black's pieces can rush to his defence quite quickly.

cxd4 is correct. This pawn becomes a target for white as its pieces need to defend both the king and pawn. Correctly played

Very nice - the sting in the tail of the long series of exchanges that began 4 moves earlier.

black isn't so bad in this position. Easily defend able, if played right  

And preventing your tactic from turning against you. I always forget to do that...

Good move. Another was `7.Re1. But the plausible-looking 7.Qd4?? would have been disastrous: 7...Nc6!

I've never thought of doubling pawns/avoiding doubling pawns as a strategy. (Looked up doubled pawns.) Thanks for that!