On a hidpi Thinkpad running Linux, it's certainly readable but I like the bold version better.

The lowercase letter strokes seem to end in non-right-angles a lot, which bothers me a bit.

Bonus picture of font rendering: https://d.maxfile.ro/amaflffqtz.png

Most importantly, the restrictions on the fonts:

Standard font: A. Limited License. Subject to the terms of this License, you may use the Apple Font solely for designing or developing applications for Apple-branded products running on Apple’s iOS or OS X operating systems, as applicable.

Compact font: A. Limited License. Subject to the terms of this License, you may use the Apple Font solely for purposes of design and development of applications for Apple Watch.

They also include additional clauses requiring Developer Program membership and Apple-branded hardware.

The font in that picture is Myriad Pro, I believe.

did you turn off font-smoothing? personally i prefer it and looks great on 10.11 DP with my 13" simulating 1440 x 900.

I too am on a rMBP (13"). I also agree that the font is weirdly difficult.

It seems to be on the thinner side, and in turn off-putting.

It looks to me too thin for an unhinted font. Its lines look like they're trying to be one pixel wide, and failing. Fonts can go much thinner when they match up with the pixel grid; as an example, here's 14pt Andale Mono on Windows 8 with antialiasing off: http://www.quadruple-a.com/tmp/AndaleMono.png

The lightest weight on the page does seem way too thin, but the heavier face above it looks great to me.

I can't put my finger on why but it feels a little cramped.