As a browser, Lunascape probably has the most to offer to web developers, who can use a single application to check how their work looks in three different rendering engines, namely Trident, Gecko, and WebKit. It also comes with features like script and Java blocking, and when using the Trident engine, you can block ActiveX too.
This new version adds a number of very welcome features, chief among which is seamless support for Firefox add-ons. You can transfer your installed add-ons to Lunascape, but you can also install new ones. This allows for a great deal of flexibility, but an obvious limitation is that the add-ons work only when using the Gecko rendering engine - pages rendered with Trident or WebKit are unaffected.
Another new feature which will surely be appreciated by web developers is the ability to split tabs within the same window, so you can easily show the same web page being rendered by the three different supported engines. This way, you can easily compare how your work renders in the three different engines.
The interface has also been given an update, but in my short period of using it, I found this by far the weakest aspect of Lunascape. It uses Qt4, but redraw performance (for instance, when resizing) is absolutely terrible, there are visual artefacts all over the place, and it doesn't follow any of the Windows Aero UI conventions - it's all custom. This means GDI-like performance, no shadows, and so on. Behaviourally, I find the interface very cluttered and overwhelming, with little to no logic applied to where items are located.
However, that's nitpicking from someone who really isn't part of Lunascape's intended audience. The main attraction here is Lunascape's triple rendering engine, which could make the browser an invaluable tool for web developers. It's still in beta, so things could still improve, too.
Lunascape is a Windows browser, and you can download the new beta from their website.