Why do yo say that QV seems to be unaffected? How do you measure this? Do you use the Task manager and monitors the memory used while QV is proccessing?
The performance will be affected by the type and amount of data fields, and your script. Also, in final applications, it is strongly affected by the data model created.
So, if you don't need more memory for your apps, QV will not use more memory if you have more memory. If you need more memory that you have installed (or have a 32 bits SO, as Daniel said), the performance will not affected too, because the paging is used too.
Do you have a server or only Desktop?
I have some apps that are bringing in 40+ million rows and are failing due to lack of memory. I'm aware of optimizing the data model and only bringing in fields needed to reduce memory usage.
I am using QV 32. What kind of "tweaks" would this need to get the memory to work?
I have a server but running these apps on the server to refresh them is inconvenient.