JS has only recently picked up speed, with vastly improved implementations in recent browser versions. It is not surprising that the one or other vendor is lagging behind, but why shouldn't they be able to catch up? So what is bad about a new IE with faster JS?

My worry is that the leading (most popular) browser is the slowest. On the web you need to work to the lowest common browser.

The least common denominator is going to be IE6 for the foreseable future whether MS releases a new version or not. Maybe by the time IE9 comes out it will be IE7.

There is always going to be a large base of people who don't update their OS until they buy a new computer and who don't replace the stock browser. IE has most of those users because it is the stock browser on the leading OS, not because it hasn't made progress. As Macs become more popular I bet you will have to start supporting obsolete versions of Safari too. Fun! :)

I only skimmed the article, but it looked as if IE9 is not that much slower than the others. I am sure they'll try to catch up before the final release.

As for IE6, I suppose Microsoft would like to get rid of it, too. I don't know who still uses it anyway - it seems to require extra effort to stick to it. Must be all the Windows 98 users?

I think the IE9, Firefox, V8 and Squirrelfish Extreme JS engines are all "fast enough". When you start performing that quickly, JS is no longer the bottleneck. The graphs the MSDN blog post has seem to demonstrate this nicely. Amdahl's Law and all that.

While JavaScript is getting faster and faster, I still don't think that JavaScript (especially DOM operations) implementations are "fast enough" yet, not even on Google Chrome. I still have to jump though hoops to get complex javascript/ajax heavy sites (approximating the richness of native apps) working reasonable quickly. There was a lot of advancement lately, but I think there's still a lot of space for improvement.

I don't think SunSpider tests DOM operations. I admit I was thinking purely of the JS engine and not of the DOM, and that the DOM is still a bottleneck. (I'd much rather the IE folks focus on DOM stuff rather than try to get raw JS any faster than they have already.)