sushi, many savvy PC folks use Mozilla (or a derivative thereof). It features tabbed browsing and ad-blocking.

Still, I prefer Safari to all other comers, even though it doesn't render some pages properly. For example, when I use Safari to check my HHMI e-mail via the Exchange 2000 web interface, I get a lot of overlapping text on some e-mails. This may just be an issue with Microsoft only thinking about compatibilty with their own browser, though.