We've started to use the HP UPD v5.4 together with iPrint client v5.74 on our Windows 7 64-bit machines. iPrint backend is NW 6.5 SP 8 with the latest available patches.
Workstations in question have the hotfixes...

A computer that is running Windows 7, Windows Vista, Windows Server 2008 or Windows Server 2008 R2 continues to use the original printer driver after you update or replace the printer driver
Print driver installation does not work in Windows 7 or in Windows Server 2008 R2 when you try to install the HP Universal Print Driver in a Novell network environment

... installed.

Printer installation takes quite a long time - approx 5 to 7 minutes. Workstations are of a reasonably high spec.

Does anyone else see printer installs take quite a long time using HP UPD v5.4? If there are any workarounds to avoid the slowness, I'l love to know what they are.