We asked Tobias Frere-Jones, the famed typeface designer who has worked with some of the world’s best publications and design shops, to offer his insights on what this change means for consumers. In his view, Apple might have made a mistake. Here, he highlights some of the challenges of deploying Helvetica Neue onto an OS abundant with small type and devices where non-Retina displays are still the norm:

Apple’s desktop and mobile operating systems have been gradually converging for some time. So it was inevitable that one typographic palette would displace the other. With OS X 10.10, Mac desktops will sport Helvetica everywhere. But I had really hoped it would be the other way around, with the iPhone taking a lesson from the desktop, and adopt Lucida Grande. Check the lock screen on your iPhone. You’ll see Helvetica there, a half-inch tall or larger, and it looks good. Problem is, there aren’t many other places where it looks as good.

Despite its grand reputation, Helvetica can’t do everything. It works well in big sizes, but it can be really weak in small sizes. Shapes like ‘C’ and ‘S’ curl back into themselves, leaving tight “apertures”–the channels of white between a letter’s interior and exterior. So each shape halts the eye again and again, rather than ushering it along the line. The lowercase ‘e,’ the most common letter in English and many other languages, takes an especially unobliging form. These and other letters can be a pixel away from being some other letter, and we’re left to deal with flickers of doubt as we read.

Lucida Grande presents open apertures, inviting the eye to move along sideways through the text. It has worked really well–for years, and for good reason. For any text, but particularly in interfaces, our eyes need typefaces that cooperate rather than resist. A super-sharp Retina Display might help, but the real issue is the human eye, and I haven’t heard of any upgrades on the way.