Bonjour for Windows
Full user review
"You have to understand what this is for"
Does what it is supposed to. But you have to understand, it is a generic networking discovery and automatic communication protocol.
None I can think of. Except misunderstanding what it is.
It is not an "AirPrint to any printer from your iOS device" solution. Certainly AirPrint could be done over Bonjour, but you are better off seeing http://forums.macrumors.com/showthread.php?t=1293865 for a discussion on how to set it up, or what I did was configure AirPrint using shared printers on an Ubuntu Linux box. With a little Google searching, and some tech knowhow, you can make it happen. iTunes uses Bonjour for network-related communication like Airplay to Apple TV, or network synch with iPhone/iPod/iPad.
For those of you having trouble with iTunes and who have hosed their installs trying to mess around with it but don't have the knowhow to fix it, Windows has a System Restore feature that allows you to restore back to a date when it was last working. It's pretty weak compared to Mac Time Machine, but it works fairly well. Restore your system to before you messed it up, and try iTunes install again.