As noted here - shahine.com/omar/ - Slashdot | Microsoft Ends IE for Mac - MS will officially lay Macintosh Internet Explorer to rest at the end of this year.
I wish it well. It truly raised the bar for a "standards compliant browser" in its day. WinIE remains a "standards complaint browser".
The below is speculation, based on bits and pieces I've picked up online - I might very well be totally wrong:
Wasn't the "missing feature" in IE5 a Radio toolbar that would have been better than the one in WinIE? It was to play MP3 formatted streams, and (may or may not have been) related to SoundJam somehow?
(But what theoretically happened is that Apple wanted to buy SoundJam to make iTunes, and didn't want to ship IE as default browser if it contained a competing Internet radio player?)