Big mistake, after all you did not have to upgrade.
Apple and Microsoft, they of course affect each other. Microsoft changed from Arial (XP) to calibri (win7), thinking a change. Calibri "looks" better especially in larger fonts like in power point, and narrower, thus not good choice for readability/writing perspective. That's why in academia it is not the font for writing/reading grants or papers.
Similarly there is a trend now making fonts thinner, narrower, etc, since "it looks good" but when you want to read and write, it is a bad option. Apple's font choice was much better than Microsoft until Yosemite, fonts were fatter and darker (bolder) looking easier for eye compared to Windows. Now they made thinner (most likely there are fashion people working for them), paler (grayer), which decreased the contrast with respect to background, and they chose helvetica, which is narrower, thus will be harder for eye if you want to separate the fonts or characters. The page might looking good if you are looking like an artist, but harder to read if you are looking like a person who just wants to understand the content.
Just look at the fonts in this page, dark gray and thinner fonts on a white/white gray background, very clever!...
