I’ve come up with a new 80/20 rule for working with Microsoft development products (but it may be universal):

• The first 80% is easy, if not already done for you.
• The second 18% is hard, often requiring an undocumented set of hacks to accomplish.
• The last 2% is impossible.

In my experience, somewhere around 83% you hit diminishing returns. At 97% you’re bleeding from the eyes.