No problems right out of the box on one desktop and one laptop, but, on my most powerful computer (Windows 7, Intel i5, 8 gig ram, Nvidia Geforce GTX 275) it takes a timed five minutes for SU to open. Once it finally opens, it seems to stay open until I grab my mouse and try to execute a command. At that point, it freezes for another 4-5 minutes. At that point, another click in the program repeats the lengthy freeze, ad infinitum (apparently).
This behavior is the same on the Intel on-board graphics (which is what’s running it beautifully on the laptop with an i3 proc.) and with a couple of other video cards, both of which are also Nvidia Geforce boards (but, less powerful than the GTX 275).
I have also completely uninstalled SU a couple of time and reinstalled, to no avail.
This strange behavior has, thankfully, never happened to me in nearly fifty years of personal computing.