This plague started only recently and breaks the web.

Established web technology offers enough mechanisms to detect the capabilities of a browser/device and deliver content accordingly. Putting "mobile" versions off to their own domains is a little bit like WAP.

What are the "pros and cons" of a "mobile device"? Comparing my three cell phones and the tablet (all of which are mobile devices), they don't have a lot in common.

Also, how would working on a mobile keep my brain from thinking "Hey, the bottom of this page doesn't render correctly, go look at the HTML source to find that one link you're looking for"?
Do we have "View source..." on microB? No. What's the reason? "Because it's a mobile device and people don't do that on mobile devices". WTF? It would be one more item in a sub-menu; how could it make a UI more complicated? And if I want to examine the source of a boken page, why would I want to wait the whole weekend until I return to my desktop? I bought a mobile device so I wouldn't need to return to my desktop for such tasks!

The assumption that people "simply don't do" things on "mobile devices" isn't logical. So the idea to strip away functionality from a mobile browser isn't, either.

What is true, though, is that on a device that doesn't feature a 1024x768 display, a full keyboard and a mouse you need to adapt when it comes to displaying a page. You also need to map what you have as input methods (maybe only a numerical keypad and a D-pad, maybe a touchscreen, maybe a alpha-keaboard) to a cleverly designed user interface. The point here is "cleverly designed". You don't design a user interface by not offering anything that would need a user interface in the first place. That's not designing a user interface, that's not accepting the challenge. (Like: Want to improve the UI for MS Office? Oh yes, just remove all functions except "File|Open" and "File|Save". Great! Such a simple, easy to use interface!)

I know. In my wording, though, a "beta" is supporsed to be more or less feature complete, at least the UI and the overall look&feel should be. Otherwise there'd be no point in testing.

It being a beta excuses that it's still slow and it still has the same rendering bugs as the first alpha (these are bugs you can report and that can be fixed under the hood), but I hardly have any hope that we'll see a functional UI in the final release. (Which is a pity, because a XULrunner-based browser would offer quite a lot of funky things to play with... It just isn't worth the hassle if the browser itself sucks.)