Australia's wine regions certainly cannot be lumped together because the differences are so large, resulting in quite distinctive wines. You only have to compare Shiraz from the Barossa (SA) versus Mornington Pen (Vic) versus Hunter Valley (NSW).
While generalizations are never perfect I agree with Halliday's vintage charts for the Barossa in that 1999, 2000, 2003 and 2005 were not the best years but 1998, 2002, 2004 and 2006 are quite a bit better with 2002 being the best for me; some of the best young Shiraz I've had have been 2002 Barossa wines.But others like Gary Walsh of Winorama don't see 2002 as a great year. Based on my experience I'd rate 2001 less than Halliday. But the caveat there is that my experince is (mainly) limited to those wines we see here in the US while Halliday looks at pretty close to everything; so I still look for good 2001's.
The other thing which is interesting, and surprises me a little, is that if you look at how Halliday rates other regions you find that Mornington Pen rates 7-10/10 for the quality of vintages from 1997 to 2006 for both red and white wines. We see very few
Mornington Pen wines here, and my only close encounter was a visit in late 2005. Wine has been made there since the 1860's but the modern era for wine there has really only been since the 1970's, and esp. the 1980's. This is a cool climate region where the most successful varieties are Chardonnay and Pinot Noir. Shiraz has been successful in the warmer areas, but Cabernet has fallen from favor and Pinot Gris is thought to have a future there. In other words Mornington Pen is still trying to find its way as a wine making area. Given the difficulties in making wine from some of the varieties (Shiraz and esp. Cab) you might expect changing vintage conditons to affect the quality of the wine produced more so than the Barossa but Halliday rates the Barossa over the same period as 4-10/10 for red and 5-8/10 for white. I believe that some years in Mornington have not been adequate to ripen all varieties (but I can't find that info). I wonder if Halliday considers that when he draws up his vintage charts!
Mike
EDIT: For those interested here are the
vintage notes for Kooyong - a top Mornington producer. Note the comments for 2002, a year that Halliday rates quite highly. To see how variable yields can be in Mornington
check out page 4 of the newsletter by Ten Minutes by Tractor, another Mornington producer.
For another take on vintage conditions over the years in Oz here is
the one from the auction house Langton's.