I'd like to see some UI add ons that look at the markets, see what's selling, high, low, avg, when selling items or buying items etc.
I'd like to see trending, like a stock ticket regarding the markets, I think that could be a lot of fun for users who like to play around with the economy. Just a thought.

I'll be playing around with making my own add ons for the game when that they release that info, so I'm excited to see what information we will have access to.