Yeah, I usually leave them there for a few days after I install an update to make sure everything's working alright before deleting them. But they're safe to delete.
Be aware that you won't be able to uninstall them using the entries in Add/Remove Programs, so you might want to edit the registry to remove those entries as well. Look for the respective keys under: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall