Every version of Affinity Designer Beta has had a lot of lag when scrolling through any swatches, though it is still usable. This happens regardless of the file that I am working on, and it has persisted through reisntallations and updates to Affinity Designer Beta. I am currently on the most recent beta (7/7/16).
PC specs:
CPU: Intel i7 5820k@4.5 Ghz
GPU: GTX Geforce 950
RAM: 32 GB DDR4
SSD: Samsung 950 Pro installation drive (where Windows and my applications, including Designer, are installed)
HDD: Hitachi Deskstar 7200 RPM storage drive (where the files I am working on are stored)
I don't think it is my PC causing the issue.