Seashell - you're not the only one thinking this, it's been hanging around my thoughts as well. In view of the number of comments saying things like "it must be your browser /settings etc, I can only report what I'm seeing.
For me, the avatars appear to be universally smaller and some of them portray less than the complete image.
The lettering under the avatars, time info above the posts and script in my mailbox etc is a light grey, which doesn't contrast very easily with the dulux brilliant white background.
In general, these features tend to make the new webpages less of an easy read compared to the old website.