It's relentless..  "difficulty" : 917.83093744!   That's 6.57 gigahash/second running right now, or about 2,000 modern (3500 khash/sec) desktop PCs.

The puzzling thing is that the dramatic rises in difficulty seems to have absolutely no effect on the dollar conversion rates.  This can only mean that the meeting between buyers and sellers is totally independent of any specific machine generation rates.

It seems likely that the people buying coins have no perceived competition in generating their own btc, so the value is immune to difficulty.

I'm just spouting off...