Well, you should keep in mind that you need to allocate slightly more than 4GB. 4GB is the minimum that QVS9 needs on an x64 OS, but a VM has memory overhead that needs to be taken into account. I forget the exact amount of memory overhead, but if you allocate 4GB, you'll see something in the ballpark of 3.5GB in the System dialog within the VM.
Other than that I don't think there are any big considerations--things should work as expected.
Vlad, the increase in memory to 8gb was a disaster. After the system came back up I had to do an iisreset to get the web site functional. It ran about 10 minutes and then the system became totally unresponsive. Had to to a VMWare shutdown and set the memory back to 4gb to return to normal operations.
Well, that's more of a sysadmin issue than a QlikView issue...I was just making a general remark about VM and memory allocations (assuming a clean install), but of course I can't predict your particular situation. Sorry I couldn't be more help.
Already deployed many systems with 16GB on vmware systems without problems, of course memory have to be present and available for the virtual machine on the vmware host. Remember that vmware tools, immediately after a system restart, execute a memory test using the baloon driver and fill all available memory to force windows to swap unecessary memory page on disk, this means that your virtual machine will use ALL memory you have configured on startup for 30 seconds circa.