Web 2.0 hype has only seen a few who have gone further from listing applications with a shiny balloon logotype.
On a developer side, as being behind the Web 2 scene, what you can spot is a whole bunch of Gecko-based browsers, KHTML and of course the mighty Microsoft Internet Explorer or, if you please, Microsoft Workaround Explorer. So why would someone name a browser like that? It has a nice interface, does tabs, lays the whole set of tabs on one page for you and takes care of your security in one go, right? Absolute niceness. Well, that is as nice as we get to develop something that's supposed to be cross-platform in respect to the open standards. That is where Acid2 comes in.
Amongst the browsers that have passed the test we can only find Safari, Opera and Konqueror all of which are small players on the market. Going through the release schedules may also add Firefox 3 to the list even though the latest alpha has not proven anything but lags, bugs and broken functionality. It definitely takes time for the undoubtedly best browser to make it. At the same time Microsoft has clearly stated that they are working towards passing Acid2 yet they have been unable to fully implement CSS2 compatibility in IE7. So not much to talk about here. At least they have reintroduced PNG transparency rendering.
Critics on Safari varies. Some don't fancy the interface, some find it too buggy, some slow. But it is definitely the most strict browser on the market providing a decent platform for a standards-aware developer. Strict in respect to the open standards. For those who compare Apple with Microsoft, that is where the differences rely. Safari is based on the WebKit framework that is open source. One of its primary components, WebCore, is released under LGPL. That is how Apple developers work alongside KDE developers.
And also, WebKit comes with a pretty nice Web Inspector: