While the user experience wasn’t that great to cancel, I didn’t have that much trouble when I cancelled last month. I just went to my account, went to the “Plans” section and clicked “manage plan” from memory.
I do agree that the “artboards” implementation is super slow, even on a brand new iMac. If the file size gets too big (and it does VERY EASILY, once you have mobile, tablet and desktop artboards) it starts to chug and moving shapes around can take a few seconds. It feels like a hack. It really does.
To add to that, if you want a cheaper price you have to lock yourself in for a whole year. That’s slimey how ever you spin it.