pixus75 on "bueno featured posts thumbnails."

hi.
i know there has been some discussion and a lot of explanations and links concerning featured images but i still don't seem to get it right, namely in the Bueno theme and when it comes to the little thumbnails in front of the excerpts of the 'Bueno featured posts' .
in my last 2 posts i have set images of the required size (490x200, not really a great format unless you are on the wp.com 'freshly pressed' page..) as featured images and they DO show up in front of my excerpts but from the theme presentation i had somewhat the impression that the tumbnails are cropped in again a different ratio, as they appear 'squarer'. in my sidebar, the pics seem tiny and the thick border (grmbl! shouldn't be imposed!) looks ridiculous.
Am I overlooking something or is my impression of the thumbnails on the wp presentation page wrong (or based on a customized .org blog ?) I would really like somebody to enlighten me on this...
tx