If you're a Republican who makes a literally false claim with a true underlying point, you deserve what you get from PolitiFact ("False," "Pants on Fire," whatever).
However, sometimes the underlying point takes clear precedence. Most likely if you're a Democrat:
With its April 28, 2016 update, PolitiFact rendered Democrat Rep. Alan Grayson's claim literally false. But Grayson received no downgrade from his original "Mostly True" rating.
Should it matter with respect to the "Truth-O-Meter" rating whether a statement is literally true?
PolitiFact's statement of principles hints that literal truth definitely counts. Examples like this one help show that PolitiFact principles are made of Play-Doh.
Update/Correction Aug. 27, 2016: Belatedly added the link to the PolitiFact Florida fact check of Grayson.
Sometimes we spot-check to see if PolitiFact is listing a corrected item on its page of corrected or updated items. Somehow this one did not make the list (archived here). The moral of the story: If you're looking for a measure of how often PolitiFact makes a correction or update, you can't rely on PolitiFact's list.