I use Firefox 95% of the time. I like Firefox as much as anybody, and I consider both Firefox and Opera to be important in more ways than just the obvious. Nonetheless, Firefox is slower with many kinds of script than Internet Explorer on Windows. I know there are many reasons for that, but it doesn’t change the fact that it’s slower.

Microsoft clearly does try to bend things toward their browser, I agree, and I think Jeff’s touched on that too. The tough part is that Microsoft (or any web application provider) often has to (or should) work around quirks in all the browsers. These details can have an unknown performance impact on the end user. So two users could use the same application on different browsers and have a totally different impression of the web application. It’s going to be a bumpy ride.

Firefox can always get better. Not better than IE – better than itself. It’s not going to improve by having people ignore shortcomings or incompatibilities.

“Both implement the standard” => The XMLHttpRequest object is NOT a standard (yet), the WHATWG has not officially released their spec. See http://www.whatwg.org/specs/web-apps/current-work/. It kills me is that people go off saying that Microsoft’s implementation of XMLHttpRequest is non-standard. THEY INVENTED THE THING! Also, the fact that it’s an ActiveX object is largely irrelevant in enterprise deployments. And watch for IE7 which will feature a native XMLHttpRequest object which will make the “ActiveX” argument entirely obsolete.

As for Opera, as I stated above, I’ve experienced my share of Opera quirks with my Ajax applications. I’m surprised you have not, but you probably have better experience at it than I.

I work for a pretty big tech company employing tens of thousands of people and they still deploy Internet Explorer with most online applications not officially supporting Firefox (yet). Seems the internal tools teams here went with a deployment scenario that can be backed by a company not an open-source community. This is what I mean by “enterprise readiness”. Not from the technical angle but from the SUPPORT angle. Maybe the Mozilla Corporation can help change this perspective, but at least from my point of view, it may take a year or more for Firefox deployments in businesses to become more prevalent.

I think the bottom line is this: Microsoft will develop their applications for the environments that their vendors demand. If enough businesses demanded that Outlook Web Access FULLY support Firefox (because of a huge Apple or Unix machine deployment, for example), and there’s no viable reason that Microsoft couldn’t do this, then I think we’d see Microsoft playing game. After all, vendors pay for the Exchange Servers and the licenses for Outlook Web Access – they don’t pay for Internet Explorer…

Other than Firefox, I haven’t seen any other XUL applications. Do you have any links? I do have strong hopes that XUL can take off (along with SVG) in order to compete with Windows Vista and XAML. Cross platform is truly nice.

Secondly, why would Microsoft allow any web application they make run on anything but Internet Explorer? MSDN didn’t (and doesn’t) work (nicely) with any browser than IE. And their newsgroup web app is similar. Microsoft are unlikely to ever be nice to Firefox – it’s too much of a threat.

As for Firefox’s enterprise readiness – that’s a different issue. Firefox is stabler, faster, and more flexible than IE. I’m pretty sure it’s enterprise ready. I now deploy it as the default internet browser on all machines I build. Yes, Windows will play nice with it. No problems.

Meanwhile, have you seen XUL applications and XPFE? Bye-bye IE.