Ever since Windows XP SP2, some printer drivers really slowed down with Windows Printing. If you have have one of those printers/drivers, a nice workaround is to use IPP instead of Windows Printing. An easy way to setup IPP Printing is by downloading Bonjour for Windows from Apple's website, and just follow the wizard as it discovers and sets up IPP.
You don't actually need Bonjour for Windows to use IPP, since Bonjour is nothing more than a discovery service. To use IPP Printing without Bonjour, try: Control Panel -> Printers -> Add Printer -> Network Printer. Then click on the button that says something about connecting to a printer on the internet. For URL, use "http://[nas]:631/printers/[printer_share_name]". As an added benefit, it should be *much* faster than Windows printing.