The scaling artifacts at 2560x1440 are noticeable but you do get used to it and the fun gameplay is still intact.
However the Steam overlay is pretty much unusable which is a pity because you are forced to use it in-game when signing up to the official Toki Tori group
(for access to the bonus levels) and looking at achievements. Fortunately joining the official group is a one-off and you can view achievements
in a normal web browser via Steam Community
. I imagine finding/chatting with friends in-game would be difficult, although I've never tried it.