In regards to the leak, the photos show the LG B's screen brightness being compared to a Samsung Galaxy S and an Apple iPhone 4. The displays of the Galaxy S and iPhone 4 are both considered to be top-of-the-line in many respects, and judging from the photos, it looks like the LG B literally outshines them both in a brightness comparison.
In the Phandroid article is a small table which seems to indicate that the LG B's display has a brightness of 700 nit (not sure what exactly that means), compared to the 300 nit from what is likely the Samsung Galaxy S. No timeframe information for release, likely carriers, or cost was given to Phandroid by the tipster.
The tweet from LG confirming the LG B also informs readers that the device will be on display at CES next year.
The amount of handset leaks coming from within LG in the last month or so (such as the LG Star, now called the Optimus 2X), in addition to LG's quick confirmation and additional details are making me feel that LG themselves is behind the leaks, and staging them to give themselves more publicity. If my hunch is true, then I just lost a bit of respect for LG. I'd rather they make an official announcement about the handset rather than fake the leaking of information.
[UPDATE] According to BriefMobile, the picture above has been photoshopped. They assert that the LG B's display is actually the Samsung Galaxys S handset's display, but only brightened. They came to this conclusion because the LG B appears to be running the TouchWiz UI that comes on the Galaxy S, plus the fact that both handsets (the LG B and Galaxy S) have the exact same display picture, except for the fact that the B's display has been siginifcantly brightened.
Image from Phandroid