The game previews are beautiful, but when scrolling down on the page with so many previews they begin to lag terribly. Not a great look.
Also, when clicking the "Edit in C3" links, my first inclination is to preview the project to try it out. I don't think it would be immediately obvious for a new user to know how to do so, so maybe a highlight on the preview button when launching from those links would be a nice usability feature for new users. After all, experienced users generally are not going to be clicking on those links.
Similar to the guided tour highlights, instead of dropping new users into the editor with no prompt (besides the somewhat unfriendly "Project exceeds free edition limitations..." message), I think there could be highlights for the preview button ("Try out the project"), and event sheet ("See the logic"), and maybe the layout editor, but that's usually already open by default and pretty self explanitory.