The one that I am most pleased about is this one:
My guess is that IE would internally append/insert the script to the document source itself and would give a number based on that single file.
Based on the rest of the article, it looks like the IE team have been examining other browsers, as there’s nothing much new there that I haven’t seen in other browsers already. The debugging application with breakpoints (et al) is available through Firebug, for example.
The third comment on the page is funny: “i just noticed today that this blog is finally script error free thats good!” – obviously they felt the need to try out their shiny new toy 😉