Well, this was the week that the world of web design was turned on its head. The release of Firefox 2.0 wasn't the cause: it's only Microsoft who can shake the industry up like this with it's release of Windows Internet Explorer 7.
It's been 5 years with the same IE bugs, but now we get a lot of them taken away and a whole new load handed back. Because of this, we once again have three major platforms to target: IE6, IE7 and Real Browsers. There has been a lot of talk about better standards compliance in IE7 but it only takes a glance at comparative Acid2 renderings to see that IE is still way off the mark. Firefox 2 doesn't pass Acid2, but its performance is actually not bad at all. In fact there is only one major class of bugs left for Acid2, bugs which will all be fixed by the reflow rewrite, which has been in progress for a while now.
Happily, the disparity between IE6 and IE7 isn't as great as I had feared and having checked a few of my websites they generally all work fine in Internet Explorer. Until I start seriously working with IE7 I don't know why that might be; either it is largely backwards compatible with IE6 and the hacks and workarounds are working, or it's much more standards compliant and the workarounds aren't working but also aren't needed. But it's probably a mixture. Some things remain broken but the workarounds are still working; other things are fixed but the workarounds are now not working, or are harmless anyway. I have avoided working with the IE7 Betas so far apart from a brief test of the first beta. It wasn't worth monitoring the situation until now. I'm not interested in Internet Explorer more than this job requires.
One thing that I have noted since the early IE7 announcements was that it would respect PNG Alpha transparency, something which I started to use years ago but which for the past two or three years I have relied on in almost every website I design. Because I've usually served a simple non-transparent replacement for Internet Explorer (usually a screen-capture of Firefox!) switched on the User-Agent request header, it's been habit to allow IE7 to get the transparent PNGs like Real Browsers do. (Actually, Microsoft did debate whether to change the format of the User-Agent string rather than just the version number, so it's lucky that they didn't or this crafty pre-emptiveness wouldn't have worked).
So what do I think of IE7? It's OK. The radical UI layout is alright but I don't know if putting your menus in hard-to-reach places is actually any better. With much more screen space for web pages (much more even than Firefox used to trumpted about back when 1.0 was released, gained by ditching the menu bar and using the tab bar for other toolbar icons), and a sleek rocker button for back/forward, it's a little bit tidier and fresher than Firefox 2.0, but it's a radical departure from old Windows styles that people are used to. Of course, I in no way recommend that anyone should choose IE over Firefox, and particularly not simply because it looks nice. In fact I would still suggest that nobody should use IE for anything other than Microsoft Update.
Upgrading to IE7 is a pain if you still need access to IE6. I've installed a copy of XP in a VMware VM so that I've got a usable copy of IE6 tucked away, and I will also try and get a standalone copy installed. Most people don't care that IE takes over your system, but all computer scientists find it horrifyingly inelegant. I loathe IE because it's insecure, and it genuinely makes my work harder day-to-day, so I also find it mildly sickening that it's always there in the background driving some application I didn't want it to.
One of the biggest changes that's happened in the past 5 years is that now, Microsoft pushes out software updates over Automatic Updates. Microsoft haven't pushed the button to send out IE7 yet, but they are planning to, and when they do we will see browser uptake like never before. It's a scary thought, actually. There could easily be a 50% jump in IE7 market share within a week, so it's entirely up to Microsoft exactly when your website will start getting crawled over by masses of IE7-using idiots and whether they will or won't be able to view your website properly.
Firefox 2.0 is also a welcome improvement. They've changed the icons, clearly to compete with the new Internet Explorer. They have been given a perspex glossiness mimicking IE7's icons. There are also many more of the minor dialogs and views such as a search engine manager, and a style for RSS feeds. Mainly this was just a wrapper for a new Gecko, which is not really a bad thing. It just doesn't need much hype, especially because many of the new Gecko features are so far ahead of IE7 that they are entirely useless on any Internet website.
If you're using a browser which doesn't run on an IE (Trident) or Mozilla (Gecko) engine, then good for you. Firefox is best for me because of its flexibility as a development tool, but I happily endorse all the other Real Browsers too.