Quoted from his what's new page:
You gotta love DNG: Playing with the LEICA M9 and its native DNG raw format, it's the only raw format I could come to appreciate.
Why? Because it's as close to a standard raw format as we are going to get.
Because DNG is a standard, I can open the files from my very, very new LEICA M9 on anything that reads raw.
The M9 files open great in Lightroom 2.5, Photoshop CS4, and yes, especially well in Photoshop CS2 from three years ago.
With DNG, you don't have to buy new software to open files from new cameras, and more importantly, I don't have to spend all day looking for software updates to be able to read files.
When you review new cameras all day as I do, I often get cameras in my hands before the software is final, so with other cameras, I often can't open raw files because the cameras are newer than the software updates! Even if an update comes out tomorrow, that doesn't help open a raw file today.
With DNG, I'm good.