built a quick spreadsheet showing average block duration and difficulty adjustments as percentages for the past 2 days using http://blockexplorer.co/ data.
only have from block 42201 (last difficulty shift) as http://blockexplorer.co/ is currently down (really wish it included total network hash rate)
with a block target of 2.5 minutes, red numbers are below the target (diff too easy), green above (diff too hard)