M. Pronay will have more first hand experience than I with the vintages of the 90's, but I can tell you a few highlight vintages from those I have tasted:
1999 was excellent for the Wachau. If you can pick up any of these Gruner Veltliner's, do it. Kamptal enjoyed a good vintage that year as well, but not quite at the level of what is generally seen from the Wachau vintners.
1997 was also very good for the Wachau, and then 1990. There were other fine vintages in between (1995 is a good example), but '90, '97, & '99 have stood out for me. On the downside, I have heard more than once that 1996 for the Wachau was terrible, and 1991 not much better.
For sweet wines from the Burgenland, look for wines from the knockout
1995 vintage. I am also a fan of the 1999 sweeties as well (particularly a few Ruster Ausbruch's that I have tried)
I concur with Mark about the quality of 1997 Styrian wines.
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