Very recently i've noticed a serious drop in performance on my feeds (aggregation). And I know exactly what it is, i've too many rss feeds! I need to sort it out this weekend, as its not good in its current state. I'm going to go through all my feeds and make sure they all still exist and put them into thought out categories, rather than the adhoc method i've been doing up till now. I'm also hoping I will sort out about 40 rss feeds which do full text syndication for my personal pocketpc news reader. The ones i've currently got are a mixed bag of crap.
Flock is my aggregator and seriously nothings happened to the project for ages. It still doesn't support rss2 feeds let alone atom. So tempted to knock up my own in cocoon sometime soon, but then again Blojsom 2.7 will also have a aggregation plugin to go with the import plugin.