As I work towards a move from Adobe Illustrator to Affinity Designer, the one feature that really makes it difficult to transition away from is the integration of Adobe Fonts within Illustrator. Essentially a large font library with useful filters which allows the designer to browse and install fonts on-the-fly. This not only keeps me from having to buy font bundles (which I find expensive and frustrating), but it also give great options during design to try fonts not currently installed.
If Affinity Designer already has something like this, I'd love to learn more as I don't see it yet. I will be upgrading to 1.8 today though to see check out the updates.