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...
I would think that as difficulty increases, this would also mean an increase in value of the coins. A 3500 khash machine currently produces 50 blocks every 13 days, which is about $3.00, or ~$0.27 per day. When the difficulty hits 9,178.3093, coins should be worth about 10x as much, but take 10x as long to generate, so I'm still making the same $0.27 per day. Of course, some of this is negated by faster computers & code.
As long as difficulty keeps increasing, I'm going to continue to buy coins.