Originally when I was looking to purchase my BDP the BDP-1USB had only just come out, so it was either with or without the juli@ card, I went with the latter -i.e. the original BDP-1 - believing it better to have both options, when I got my BDP I simply hooked it into my BDA-2 via AES/EBU and never touched it and it sounds great.
However with all this talk of the new audio device in the BDP-2, I decided I might try USB out to my BDA-2 and I can say that the USB and AES/EBU sound practically identical to me, I haven't done any real in depth listening across a broad range of music but they both sound great to me, I wouldn't be able to tell you which input was currently being used if I was blindfolded.
As mentioned before the BDP is nothing like a computer, I have tried multiple computers with multiple dacs via USB and optical and nothing comes close to the BDP. I've used the BDA-2 via USB and Optical to a Mac Pro and Macbook Pro and neither sound anything like the BDP even with the exact same audio files.
So I can't specifically quote the BDP-2 as I have the BDP-1, but I would be more than happy if I had USB out only, but this probably has to do with the DAC, as I've heard other dacs that can't come close to the BDA-2.