Useless, there are a couple of pay products out there that are very good, and there are any number of plugins and freebies that work more or less, depending on your way of looking at things.
I chose to use a freebie one because I liked the code and knew I could fuck with it slightly. If the project works out (and it appears to do okay) I will likely move to a pay solution (like rss2blog or similar) so that I can gain even more control over the content on the page.
Aggregation is difficult mostly because different bloggers have different styles of content, and not all of it is easily digested. It is an interesting project, put it that way
Alex