I'm a big user of Twitter (@steverumsby), and so when the new SCN was unveiled and it had an activity stream much like Twitter I was immediately drawn to it, and almost all of my use of SCN is via the Activity stream. I follow people (80 of them right now) and places (26 currently) and so see everything posted by or in them. It is a good way to make sure you see all (well, most) of the new stuff that appears here that you're interested in.
There's another advantage too, though. When people you follow like, rate, or comment on content, that information appears in your activity stream, even if the original content is in a space or by a person you don't follow. When people you follow follow new people, that appears in your activity stream. In other words you see not just the stuff that interests you but also the stuff that interests people you follow. This is a great way of discovering new people and interesting content you wouldn't have otherwise found.
One of the new missions in SCN is to follow a few people, so if you haven't done that yet, do it now and give the Activity stream a try. See what you can discover!