Being able to watch tags in del.icio.us is great, but repetition is a killer. Subscribe to the RSS feed for a popular tag and watch as the same link keeps coming over the transom. Overnight, I can have upwards of 60 links added to my inbox, many duplicates from the day before. I need another wrapper feed to collapse these guys!!
Next generation aggregation tools will need to have distillation and summarization facilities baked in. I don't think they have to be able to solve AI hard problems, but the interfaces need to be very good.
Speaking of wrapping feeds, wouldn't it be nice if del.icio.us tag feeds could call home, login as you, and check to see whether you've already saved and tagged a link?
Aggregator as platform again. Maybe I'll have to get one of those Web based aggregators and hack on it in parallel to my bloglines reading.