I think Safari for Windows is essentially a waste of time..
I rather see Apple concentrate on what they do best, not create new Windows apps...
This one I can actually see being a good thing.
If you think about it most of us are tied to some sort of PC for work or gaming. Many of us perfer our Macs for our home time, or to use while browsing and other internet activities. Given that it's nice to only have to learn one browser to do your browsing having Safari available on both platforms will keep some people from switching to Firefox to remain consistent across their computers, thus increasing Safari's share of the browser market. I know quite a few Mac users who use Firefox so they can stick to one browser on their Windows and OS X boxes. With the availability of Safari they might change their minds. Especially if Apple comes up with a good way to sync the Windows and OS X Safari versions. Maybe something using Bonjour.