Thanks for this analysis, MNb – took me a while to get around to looking through this, and I’m not sure I grasp all of it fully, but I certainly like 12…b6 13.Rb5 Bc5.  It does indeed show me that 12…b6 isn’t at all bad – it looks odd, but seems fine, as has been mentioned by others here.  The other lines get rather messy but also seem fine, although I’m not well qualified to evaluate…..

I'll look at the lines Paul gives later, thanks.

I still really like the IZ, and intend to work more on understanding it, but whilst I’ve been searching for something else (more ‘solid’?) I’ve found that there is so much work to do in other defences, the Dutch just appears on the board so much more readily…..  

'Ugly' moves - indeed, a good move is a good move before it is any other kind of move, to repeat one of Rowson's moe quotable aphorisms.

I seem to remember that my computer thought that 12...Qd6 was a good move.

With regard to Simon being outmatched, there certainly isn't 300 points between the two: SW's completely creamed Agrest for one on the black side of the Dutch and had Korchnoi grovelling recently. Of course Shirov is much stronger, but I think it's being overstated here.

I've been analyzing 12...Bc5 on my own a bit, and I think it's quite interesting.  If 13. Rb5 b6, we've transposed to the line that MNb gave; I think Black is fine here, maybe even slightly better (but that's probably just my personal preference).   

I don't think 12...b6 is an "ugly" move; once the rook moves from a8 there shouldn't be any problems on the long diagonal.  I admit it's a little ugly in that weakens the light squares, but it's probably necessary sooner or later to keep the rook on the b-file at bay.  Also, don't forget, that chess is relative; Black's queenside may be slightly weakened after 12...b6, but it's still nicer than White's!

  I felt the same about 12...b6.   

Great book, 'Chess for Zebras'.

OK, I'm not at all worried about the viability of the line as I've only faced it once - I play most of my games online and at quite a 'casual' level, so most players if they even get to 7.Nc3 don't know much theory beyond there (like myself) and usually opt for the more natural looking recapture with the Queen.  I was just interested to see what Williams would do against a player ranked so highly as Shirov - I know Williams has beaten GMs such as Joe Gallagher with his pet defence, but with Shirov being even higher up the food chain I thought it might be worthwhile me trying to understand what was going on here.  As you say, I would guess that Shirov knew exactly what Williams  was likely to play in this line - but even if he didn't I guess he would likely trust in his ability to pull in the whole point against a player he outranked so much.  In Yermolinsky's book he says 'You give me a good position after the first 10 moves with plenty of pieces on the board and I'll find a way to outplay anybody 300 rating pounts below me'.  Maybe that was likely to be the case in this game however the opening went, with all due respect to Simon Williams. But it has been useful for me to hear your comments, especially about the amount of compensation for the exchange, something I often struggle to evaluate.   
I see the point about the e5/f5 pawn duo and the Bishop.  So I looked again at it with the help of Fritz 9, which seemed to prefer 12...Qe8 or 12...b6. 
Anyway, thanks for your help and comments.  They'll prove useful for me should I run into this line, I think.

"wouldn't 11...Nxe5 have been better for Black than the game move?"
I doubt it. One of Black's goals in the IZ is that nice pawn duo on e5/e5. This controls the centre and opens the possibility of a kingside attack with f5-f4.
After 11...Nxe5 though Black will have problems activating the queen's bishop.
Just my 2SRD thought.

Thanks guys.  I looked again at the position and your comments.  The move that came to mind for me was 12...Rb8, but it doesn't really look right.  Maybe by that time I just didn't like Black much anyway.  I think MNb's comments seem about right.  

I'm not sure that this is in accordance with the general strategy of Black's central pawn play in this opening, but wouldn't 11...Nxe5 have been better for Black than the game move?  I think I prefer this move myself, but I'm not sure that it is the right way to play the position?

I wouldn't be too worried about the result of this one game; no offense to Mr. Williams, but he was pretty seriously outmatched.

I play this line as Black with good success, and while I've never had the position after 12. Rb1, I think the obvious place to look for an improvement is at move 12; I bet Black can do better than 12...a6.  My first instinct is to just play 12...Qe8, because Black will almost surely have to play this move anyway.  12...Bc5 is also worth a look, when a later Rxb7 (after the light squared bishop moves) can be met with ...Bb6.  I think even 12...Rb8 looks better than 12...a6, though this is only a cursory inspection.