I didn't have good stability until I upgraded all the way to 5.5 tbh. Setting up the vCenter appliance and getting web client working took a little time but I have a VM booting with 8GB RAM running accellerated apps in XenApp reliably now.

I was having loads of problems with the passthrough card not being used for the remote apps, instead being load balanced with the VMware display adapter. Through some iterative troubleshooting (AKA trial and error), I found that if I booted the VM with the VMware display adapter enabled, and then disabled it after Windows starts up, then everything runs over the passthrough card. And if I enabled the VMware adapter prior to rebooting the VM, it rebooted without going to the 'safe mode' adapter. So I set out to automate this.

When I tried removing vmware tools altogether and deleting that vmware display adapter, I ended up with a 'Standard VGA adapter' getting added and my FirePro display was not recognized at all.

My current workaround is to use the microsoft utility DevCon and scripting - http://support.microsoft.com/kb/311272

I ended up not using the download from that site... had to find a true 64-bit version, not the itanium version they provide.

I have used devcon to identify the device id, and it can then be used to disable or enable the device. In this case, the vmware display adapter. So I've ended up with two scripts, a shutdown script that enables the vmware adapter prior to restarting the server, and a startup script (stored in ProgramData startup path) that disables the vmware adapter after windows boots. In testing, this seems to be working reliably with the remote apps using the FirePro card 100%