>XML strings are very slow due to their size and having to convert them back and forth ( has been our experience in VFP just now started to experiment with .Net/Sql ). All we do are dynamic queries. I would guess less than 15% of our queries are coded. Our users are allowed to pick their own columns, filters, and sorting in all our grids and reports. Very fat client.
We don't seem to experience any slowness using XML strings and DataSets. Perhaps it depends on the application and what it's intended useage is.