Do I really need Bonjour on Windows?

From Apple's knowledge base article about Bonjour on Windows (my emphasis):

• iTunes uses Bonjour to find shared music libraries, to find AirPort Express devices for streaming music to, and to find Apple TVs.
• Safari uses Bonjour to find devices advertising web pages on your network. Many of today's network printers, network cameras, and wireless gateways provide a web interface for status and configuration, and many of these devices (especially network printers) now advertise those web pages using Bonjour, to make them easily discoverable in Safari.
• Internet Explorer, via the Bonjour toolbar plugin, also provides easy discovery of Bonjour-advertised web pages.
• The Bonjour Printer Setup Wizard uses Bonjour to discover and set up Bonjour-advertised network printers.
• Adobe's Creative Suite 3 applications use Bonjour to discover digital asset management services.

If you don't use any features, then removing Bonjour won't cause you any trouble (except perhaps Apple Software Update might offer to install it again...)

Furthermore, this page has some instructions for more throughly uninstalling Bonjour.

You are able to use "[computer name].local" domains all over your network. This also applies to Apple mobile devices and other hardware (I have: Mac Mini, Western Digital NAS, HP printer and Linux laptop -- it has its own Bonjour called Avahi).

Please support adoption of the Zeroconf protocol and report bugs to Apple, because they give us an opportonity to drop the horrible NetBIOS technology and to connect across different platforms.

You don't need it, about the only thing I have ever actually used it for in a Windows machine is to enable printing to a printer attached to my Airport Extreme. In fact because of the unusual port range it uses, I have actually encountered issues with VPNs that have refused to work properly until it is uninstalled, so I actually remove is as a matter of course.

Of course if you do magically require it later down the line, you can always install it as an individual package.