We are using shapefiles with a large attached database to it (162 Mb for 133000 features). Opening this shapefile on a remote server takes about 5 minutes whereas DivaGIS takes 7 seconds for the same file.
My suspicion is that QGIS loads the entire shapefile to client and stores it in a temporary directory before rendering it whereas DivaGIS picks up the geometry, renders it and opens the .dbf file on the remote server.
My question is: "How does QGIS handle files and how can I improve this and / or can it be improved?"
(I have once read an article "QGIS on steroids" but I have not seen any improvement since QGIS 1.6)
Working with Postgis improves this a little bit but it doesn't come anywhere near the speed of DivaGIS.