I would very much enjoy being able to create custom feeds as Reddit currently allows, i.e. dump multiple subreddits into a single feed. For practical implementation, you could mimic this functionality by allowing the user to add tags to subscriptions (client-side only) and add these filtered feeds somewhere near the location of "Frontpage".
Frontpage (all subscriptions)
- Pics (all Frontpage subscriptions tagged Pics)
- Tech (all Frontpage subscriptions tagged Tech)
- PORN (all Frontpage subscriptions you obviously don't have)
- ...
This way I won't have to scroll past 200 cats if I want to read up on the latest Android news (which appear to be released less frequently than pictures of random cats).
Thanks in advance.