I was using the Twenty Ten theme and decided I wanted my category pages to show the full post, not just the first few lines (and without any images). So I changed to Twenty Eleven today. Not sure I like it as much, the pages seem narrower, though I did a comparison and the amount of text on a line was the same. A small bonus is that the header image is a bit deeper, so the cropping is not as extreme as in Twenty Ten. Gives more flexibility in using photos for headers.