Cybernet reminds us that this wasn't quite unexpected -- Steve did say that Apple had made inroads on Windows with iTunes, and that they planned to use those inroads to send Safari around. The only problem is that, while yes, the button and the text do say "Install," the program is usually used for "updating" software, and so getting new software with the deal wasn't something a lot of users expected. And users who don't do anything but the default (I can guarantee you that, since I bought my mother an iPod for Christmas, my parents now have Safari 3.1 installed on their PC, despite the fact that they still aren't quite sure how that Firefox I installed for them works), are basically getting software they didn't plan to have.
Sneaky unwanted software scheme, or just a not-so-subtle hint to Windows users that they could be using a better browser? You decide. I just know that I'm going to be paying a little closer attention to exactly what my Software "Update" is updating (or "installing") from now on.
Thanks to everyone who sent this in!