I'd like to share some feedback having tried to use workboards for project management within my organization. I'll start with a UI surprise: dragging tasks up or down in the list changes their priority. I wasn't expecting that, even though I read about it in T1344 recently.
I suppose this could be addressed in the UI somehow, making it more clear as the dragging is happening that the priority is going to change. Already priority is associated with color: perhaps the color can change to reflect what the priority will become, and when it's going to change, an animated halo draws attention to the changing color. Or, since there are only a few priorities, there could be rows for each one, making the workboard a matrix, where it will be obvious to the user that moving between rows is just as relevant (in that it will change some property of the task) as moving between columns.
But, I also think that maybe priority should be independent of order. Two reasons:
Firstly, a task may be in multiple workboards, and it may make sense to have different orderings in each. For my experiments, I had created an "estimation" project and associated workboard with 1, 2, 3, 5, 8, 13 columns. The idea is to play planning poker to estimate the effort required for tasks, then drop them in the corresponding column. I can't think of any particular way I'd want to order tasks in the workboard. If I could, it probably wouldn't be by "priority".
I can think of an alternate ordering for a different kind of workboard, say one that represents a sprint. I may, when planning a sprint, decide that tasks should be addressed in some order. This order is likely not priority order, either because of dependencies between the tasks, or because of another reason: there's "important", and there's "urgent", and they are not the same thing. I don't know about how everyone else works, but in my organization, this is a common problem:
We decide that we need to develop a frobnicator because we are frobbing things all the time. We decide that it's important, because we stand to save so much time. We make a note to do that real soon now. Then, Bob says "I need those TPS reports for the meeting tomorrow!" We decide that's urgent, because it must happen soon. So we make a note to do that too.
A week later, we discover that we've successfully addressed the scads of urgent tasks that have come up, but failed to make any time to address the important tasks.
It's hard to plan because it's easy for someone to say "I need this urgently", but it's hard to tell them "OK, but we don't have time" when you don't have a way to see how much time you need to budget to address important but not urgent work.
I remember reading something in particular on this problem, but I can't find it. Anyway, if you search for "important versus urgent" you can get plenty of stuff. Though a lot of this stuff downplays the importance of "urgency", there are legitimate things which are urgent, especially when one commits to delivering things on time. A deliverable for a particular client may not be that important (it's just one client), but it becomes increasingly urgent as the deadline approaches.
If workboard order is not the same as priority, this gives me a way to indicate visually a two-axis state of "urgency" and "importance". I can choose to denote one with the "priority" property, and another with top-to-bottom ordering on the workboard. Furthermore, I can have arbitrarily many other orderings by creating more workboards, with the ordering defined by some property relevant to that workboard.