The "upvote" icon is not intuitive and perhaps even counter-intuitive. The arrow turns from dark to light when I vote for an idea, which to me makes it seem like I haven't upvoted it.
Interestingly, it's backwards (correct?) on the "New Ideas" section of the forum! The arrow is dark when I've voted for something, rather than light when I've voted for something. This is actually more intuitive. PLEASE CHANGE TO THIS EVERYWHERE!