The amount of STEEM power that has been up-voted per user in addition to the number of up-votes.
Ability to subscribe to different users content/updates/etc. So I can social engineer dantheman's interests to precog his upvotes.
Ability to follow Tags/Topics
A form of reputation for content creators. I see many videos of people that post to Youtube, being submitted by multiple users. I am undecided on the use of plagiarism, however the ability to give the original creator rep so they rank higher may be the solution.
Search functionality that is more effective than the out of the box Google cookie cutter being used now, gross.
Additional in-line UI tools for use of markup, similar to creation of a WordPress Post. To make things the prettiest.
Connectivity to decentralized file storage like IPFS, so I can upload a file directly instead of having to host it on the internet first.
Ability to move STEEM, SP, SD to Cold Storage (Not sure on the technicals of this)
Customizable User Landing Pages - However with Restrictions to space, number of images, characters. Restrictions harbor creativity.
Functionality to ignore certain keywords, users, tags. Ugh like introduceyourself... mostly kidding.
An avatar, snapcode, profile pic like thingy. You know I like want to be unique.
Some of the metadata housed on steemd.com could be cool, if you don't know about that - check out me here yo https://steemd.com/@dekrypt
Last of All User Membership Level - Don't be holding back them Gold Stars, those guys worked hard for that.