Looks like the difficulty took another big jump up, and since the average blocks-per-hour is still above 6, could the max difficulty adjustment rule been hit? I know that the difficulty is limited to "a factor of four" but I don't know exactly what that means in practice, nor how that might be reflected in the adjustments.
Also, what does this mean for the size of the bitcoin network? Can a relative number of 'average' cpu's be estimated from this data?
No, since we are increasing speed the speed at the end of the period is higher than the average power over the period which is what is used to determine the new difficulty. So even at the beggining of the new period we are faster than 6/hr by the difference of average
speed of the last periodLook on the statistix page, we've been around 8 for over half a year, it's because we're increasing the whole time.