There are definitely two schools of thought on this one – we are NOT taking sides.
The first is that Apple is using its market leading position in music jukebox software to push its browser – like Microsoft used its market leading position in operating systems to push IE a few years back. While effective, it isn’t really fair to the Firefoxes and Operas of the world who don’t have that leverage to fall back on. It is also a bit misleading to say it is a "software update" when it was never installed in the first place. If you were using Microsoft Office on Mac and an update came up saying "Update your Internet Explorer (which you don’t have on your machine) for Mac to 5.2.3". Would you be happy?
The other school of thought is that Apple isn’t forcing this on anyone. There is simply a Apple (not iTunes) software update that is letting Windows users know that there is a web browser available for them, should they want it. Google does this in one way or another with its Macintosh applications. So does Adobe. No harm, no foul?