I like the idea of @Kevin Weber a lot! At least the part with 10 levels of priority showing inside checkboxes.
In fact, wunderlist tasks already have statuses "not started" and "done'. So adding the status "in progress" would help. It could be implemented by adding third state of checkbox like - empty checkbox means "not started", blue checkbox means "in progress", checked checkbox means "done". So to complete the task you should click status checkbox twice. If one more sorting option is be added (by statuses) it will be nice solution...
For tags, colors, due date, task creator, tasks with new comments etc. Smart lists are the cool thing for productivity!))
but cannot see the mock-up in ipad safari :(