The examples were just hypothetical and not particularly important, but as steemians know, after logging in, there you are: go for it, and good luck. While using the service you don't have a lot of visibility into the metrics of your or anyone else's account, or content, without simultaneously referring to at least one other service like https://steemdb.com (which is pretty much the dashboard we have), these are just common examples:
- quantify, explore and navigate content by tags
- view previous versions of edited content
- know current voting power
- see a count of inbound/outbound votes or comments (per article?)
- review graphs of post, comment, payout over time

If you're a writer with fairly consistent rate of output it would be useful to be able to review an interactive line graph showing articles posted during `<period>` where incoming comments and votes and payout could be overlaid; where did that spike come from? Change period to 48hr starting `<date>`, tick the check box for comments, turns out a recent comment got 147 votes, a couple of them on the larger side. How's my interaction with others looking? Check boxes for outbound votes and comments; I need to spend more time looking at others' work.

Basically steemians end up flying blind or using multiple web services, which can make it hard to track output/performance or even peruse the content. Important basic elements of steemit are absent in the web GUI, such as current voting power value shown on the 'ribbon', and a 'previous version' link for edited content.

Just ideas, at any rate. For now steemians have to settle for scrolling down long lists hoping to not miss something while trying to keep a heuristic map in their head, and/or referring to multiple external services.

I probably shouldn't have used the 'killer app' term, I did so glibly, but the term should be reserved for the eventual app that facilitates directly posting from the internet (or wherever) to steemit whatever is currently under the users finger and that may just kill steemit with spam and lawsuits.