Interpreting ProTop3

If I'm often seeing low numbers (usually in red or blue) in ProTop3 for my BIW/AIW Write%, does that indicate room for improvement? Should I be concerned? What kinds of things should I look at to diagnose and treat?

In some ways that is there mostly to show that the coloring of metrics in response to thresholds works ;)

Beyond that -- if you had a lot of BIW activity (lots of notes being written) and those percentages were also low you might want to investigate why it is that the BIW is not pitching in and doing its fair share.  I think my first impulse would be to look at the bi cluster size and the interval between checkpoints. 

The rest of BI write activity can be done by broker (_UserIO._UserIO-BiWrite where _UserIO-Id eq 0) and by AIW (where _Connect-Type eq "AIW"). If the sum of BI writes by broker, BIW and AIW is almost 100% then it's, IMHO, fine for performance. How the writes are spread between them is less important.