Dev Build 2169 is out now.
Text positioning on OS X has changed to match typical Core Text output (as used by TextEdit, Terminal, and Safari). For anti-aliased fonts, this means rounding glyph positions to pixel boundaries for small font sizes. The previous behaviour of never rounding positions is available via the no_round font option. Aliased font rendering has also been changed to use a different set of rounding rules, which should now match the terminal.
Please let me know if you find any font or size combinations where the rendering doesn't match TextEdit.