Datasets and Performance

Question

We have been using o-o techniques when developing our Windows Forms applications and have layered our applications so that each has an Application Layer, Business Logic Layer and Data Access Layer, we have used datasets to read and persist data to the database. We are about to re-write one one of the applications as an ASP.NET application and can re-use all our classes from our Business Logic and Data Access Layer with no changes, however I have read some reports of people having performance problems when using datasets with web applications. I was hoping that as long as we do not populate the datasets with huge amounts of data then all should be OK The web server will be used by up to 1000 people. Any comments/problems with performance when using datsets with ASP.NET would be appreciated. Thanks John