I have been using EpicWin since the program was first released, and it has been exactly the program I was hoping for. While it is not a silver bullet for productivity, just like Supermemo, EpicWin requires self-discipline to be useful. Here is how I use EpicWin.
I keep a task-list within Supermemo (A very, VERY useful feature that I will make a post on eventually). I use the task list to organize and prioritize the various things I have to do. Using this as a guide, I enter the tasks into EpicWin and assign them point values that reflects their importance in Supermemo's task list. Then I accomplish the task. Keep moving onto the next task until all of the tasks are completed, and great peace of mind is achieved.
So basically I use Supermemo to create a "hit list" of tasks, and EpicWin is my task "Assassin" to execute them.
I also use EpicWin to give myself "achievement points" for real life. For example, doing dishes right after I finish eating grants me more points as compared to letting them pile up and doing them later. Also, let's say it snows during the night, and I know that I should shovel the driveway sooner rather than later. Big bonus for doing that! I really don't want to go jogging this morning, but I'll gladly do it if some points are involved. In this manner, EpicWin serves as the "nudge" I needed to get certain tasks done when there wasn't much of an incentive to get them done. In this manner, it has also been useful and (in my eyes) a success.
Although the program/game that I had in my head was slightly different than EpicWin, EpicWin fills the task-list RPG-sized gap in my life, and I'm very pleased with it.