<A target="_blank" href="http://www.pcworld.com/businesscenter/article/221919/why_internet_explorer_9_will_never_be_number_one.html#tk.rss_news">Unlike some other versions of IE, IE9 isn't "part" of an operating system upgrad</A>e, which will limit it's deployment. Interim upgrades never gain the same market share as those tied to an OS replacement.