I always thought tabs were an Opera invention, or maybe one of those IE shells like Maxthon or Neoplanet? IE5:mac was a fantastic browser though and was widely regarded as having the best CSS1 conformance of its time, as well as some cool features like an eBay auction tracker sidebar that seem quaint today but were very useful to me at the time: https://alistapart.com/article/ie5mac/

On the flip side, the only time I can remember hearing an entire crowd boo Stebe Jovs was when he announced that IE 4.5 would ship as the default browser in Mac OS 8: https://youtu.be/WxOp5mBY9IY?t=142