IE7 security > Firefox? Hahahaha. We'll see. I've been hearing the same story after every major MS security hole "we are seriously focusing the whole company on security", then, viola, more holes found. A never ending stream of them.
Explain how RSS support is better in IE7 than Firefox.
Broken features on GPUs led to those advertised features not being available to their paying owners. IE users (the vast majority for the past 6 years) did not experience any broken features or buggy sites, nor did they pay specifically for IE. This issue hasn't even come up until recently because of Firefox's relatively large adoption due to the insurge of malware and viruses using IE's vulnerabilities.
Number one, the issue of broken features is one for developers, not end users. It essentially means developers need multiple rendering paths and workarounds, and it is a huge problem with complicates game development. IE's various incarnations (4,5,6, and now 7, also, Mac IE's completely different rendering engine) vastly complicate web development, and this was long before Firefox existed.
We've gone over this plenty of times, about how shoddy SM2.0 implementations have held back game development and uptake of that technology, with the end result is that gamers are not seeing games that look as good as *they could have been*
This causes much pain for developers who want to take advantage of more powerful browser features to design more interactive websites (like Google Maps has done, and all of the other AJAX oriented sites) I don't think you have any idea of the level of extra effort that goes into making sure a website works in IE4, IE5, IE6, Mac IE, Firefox, and Safari. Developers are forced to punt: either they render everything to the lowest common denominator, or they have fallbacks for all of the bugs (primarily in IE versions). This is alleviate somewhat by cross-browser script layer frameworks, but it is a major pain in the ass to QA validate a website now.
I'd rather IE7 not change ANYTHING in their rendering engine until they are fully CSS compliant. All they've done is create yet ANOTHER rendering path: IE4, 5, 6, 7, and a hypothetical IE8 that is bug free.
The end result of Microsoft's shoddy coding practices is that truly innovative use of web standards like XHTML, CSS2, DOM2+, et al, has been delayed because MS has made it a pain to support by creating a huge legacy installed base of buggy, insecure, fucked up browsers.