This might already be a known issue or work in progress feature, wanted to raise this just in case. The rendering in 259 is much smoother when compared to 260 with the same font. If you need any more information, please let me know and I will update the issue.
Hi, i have also noticed the same problem:

On the left side we have vimr snapshot 259 and on the right latest snapshot 267
mac OS High Sierra 10.13.3
Same here, it's especially bad on 2K external monitor.
Yes. Terrible rendering of fonts still in 267:

(left VimR; right vim in iTerm2)
Same issue. In my case, only current line with set cursorline is antialiased.
Any updates on this issue? I'm also having it since a few releases.
This font issue is enough reason for me not to update VimR...
With v0.20.6-261 (for accuracy, please open the image in a new tab):

With v0.21.1-269 (for accuracy, please open the image in a new tab):

In non-retina displays, legibility is terrible for me. In retina displays it's still usable.
Could you please try http://taewon.de/VimR-rendering-GH-612.tar.bz2? I reverted a background coloring optimization which seems to cause this. If this build is OK, then I'll release a bugfix version.
@qvacua I downloaded that version and the latest pre-release and it is much better 馃憤

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Could you please try http://taewon.de/VimR-rendering-GH-612.tar.bz2? I reverted a background coloring optimization which seems to cause this. If this build is OK, then I'll release a bugfix version.