I'd love a recurring automatic payment charged to my card for a paid account. It would be easy as long as there's an obvious way of cancelling them. I have this for my Webshots account and it's nice to not have to worry.

And my favourite Dreamwidth feature (so far) is being able to search my own journal by keywords. Sometimes I'm looking for an entry but don't remember exactly when and don't want to go through all the tags. (My second favourite DW feature is how many more icons we get than over at LJ!)