I’ve been working on activity streams as well (the activity tab you see in that thar image), but I’m not 100% happy with them. They look nice enough, but I’d like to work in slightly different displays for different types of activity.
A good example of this is voting – since currently all the activity streams stem from a default set, which renders whether you’re on a user’s page or not, it also renders their avatar alongside the content of that particular activity. This is great for generic lists, and works fine for activities with content (such as forum posts, page content additions etc), but for small things, it’s a big ol’ waste of space, both horizontally (due to page width) AND vertically (thanks to the avatar).
It’s a bit of a quandary. I’ll mull it over while working on other sections, I think.