There are a number of things that are still remaining to be done on this. This list will change as I get new ideas and suggestions, and will shrink as things get added. To see what has been added already recently, take a look at the changelog. This may include things that have been put into the development version, but aren't yet in the released version.
If you want to have a go at doing any of these, see the Development page for details. If you think there's something missing, see if it's already been suggested, and if not add it to the list.
Soon I hope to get a 1.0 release done. Currently there are a few things remaining before I consider it complete. These can be found on this page.
Things to implement as time and inclination permit: