Hi Juan,
one thing I miss in PI is a profile tool. With this tool you draw a line and the tool window shows the RGB (or L) values along the line. AIP4WIN has this tool but it's broken for zoomed views. Fitswork has a nice version that I used here:
http://gallery.tungstentech.com/main.php?g2_itemId=431Now of course I could keep on using Fitswork but I think you can do some cool things with this tool. I think it would add some more -measurement- capability to the set of -processing- capabilities you already have.
A profile tool would be handy to examine dynamic range in seemingly even structures like the centers of bright galaxies. It can also be used to measure the effectiveness of flat fielding and DBE.
Not a high priority item but something to consider for your todo list