Although Apple's introduction of Safari caused Microsoft to put the Mac version of its Internet Explorer Web browser into "maintenance mode" way back in June 2003 - ceasing development while pledging to make bug fixes or patch security loopholes in the even-then-aging browser - Internet Explorer on the Mac has now officially come to the end of its life cycle. Microsoft stopped supporting the Mac version of Internet Explorer on 31-Dec-05, and will remove it from its Mactopia Web site on 31-Jan-06. (So grab a copy now for your archival software collection or stable of programs for HTML testing!)
Although Internet Explorer remains a dominant browser for Windows (where it's creeping toward a version 7 and served as a focus of Microsoft's long antitrust battles), Internet Explorer on the Mac was always a somewhat distant cousin, having been birthed back in 1996 by what would eventually become Microsoft's Macintosh Business Unit (MacBU), made up of genuine Macintosh programmers at a time when Apple seemed to be careening towards dissolution. Even its first beta release (version 2.0, which I reviewed back in TidBITS-311 using my shiny 28.8 Kbps modem!) one could see Mac-centric design features, and its last major revision (which Adam reviewed in TidBITS-523 back in March 2000) pushed to offer useful and powerful features for the time, like a scrapbook and auction tracker, plus a serious attempt at a platform-agnostic page rendering engine.
Internet Explorer made the jump to Mac OS X early on and, like a thorn in Apple's paw, remained the operating system's default Web browser until Apple shipped Safari in early 2003. Despite some longstanding, glaring issues (cookie management, anybody?) and never having been updated to offer features like tabbed browsing, pop-up window blocking, and RSS support, Internet Explorer's integrated scrapbook was a phenomenally good idea, and, to my knowledge, its auto-completion feature has been matched only by OmniWeb. Internet Explorer also provided the only built-in access to suffix and file-mapping settings in Mac OS X: now, as installed, Mac OS X enables users to configure only default email and Web applications, and you can't even do that within system-wide preferences but must instead adjust those settings within Mail and Safari. Users with more sophisticated needs must use programs like RCDefaultApp, MisFox, or More Internet.
So, it's hard to say we'll miss Internet Explorer: after all, like Netscape, it stopped coming to Macintosh parties a few years ago and hardly ever writes or calls anymore. But there was a long period - preceding and during the so-called Internet Boom - where Microsoft led the pack amongst Mac Web browsers and jauntily kept getting better, while Apple was struggling for air and Internet Explorer's main competitor, Netscape, publicly writhed in its own agonies and drifted further away from the Mac. I may not be speaking for everyone here, but Internet Explorer and the Mac walked a long way together, and some of it was uphill in the snow, both ways, on some very cold days. So, thanks, IE: ya did good.