It seems that Dave Winer had a chat with the human aggregator (Scoble) and came away understanding why you'd like to integrate an aggregator with e-mail. Dave's two takeways were:

1. Since it's integrated with email he can easily forward an item to people he works with via email.
2. He has a folder where he drags items he wants to write about later.

Dave prefers Radio's blog like aggregator, which I've never used, but I understand that it puts all the aggregated stuff into a single HTML page, so that you can read it fast. I like that. That's why I use FeedDemon. It gives me that big HTML page so I can do the fast scan, and it takes care of takeaway #2 because I can create a news bin (or bins) to use as holding pens for items. Takeaway #1 would be a small matter of programming to implement, and I suppose that getting it really integrated to the mailer would be difficult.

I'm of the opinion that aggregated RSS data is a little different from mail or Usenet news, and so I want a different user interface for it. Certain kinds of e-mail integration is nice, but I also want integration with the rest of my PIM-space, which is possible with something like Newsgator. I'm pretty sure that Greg is hard at work on this -- too bad I hate Outlook.

Actually, I think it would be interesting to see a blog style style aggregator with a UI like this one. There's room for all kinds of stuff. The old PARC Perspective Wall or Cone Trees are some examples that easily come to mind as food for aggregator UI's. UI's are so stuck in the mud.