Fractional font sizes can't be input using the "Preferences" dialog
I opened the "Preferences" dialog, focused on the "Font Size" spinner in the "General" tab, and attempted to type in "9.5". The spinner transformed the input into "95" instead.
Because font size influences the size and readability of the entire UI, giving the user fine control over the font size would be beneficial. The layout difference between, say, a 9pt and 10pt font is significant.