Overview
You've been using Trello for the Kanban board, and now you are reviewing Kanban boards within FogBugz. The biggest issue for some of your users is they do not want to have the Kanban items linked to cases inside of FogBugz but use it more for project management or status where they can just move "post-its" around without populating tons of case information (more of a high-level thing).
Solution
You can utilize the Kanban board without adding any case details, just the title (but that is also needed for a Trello card). Once the card added you can easily drag-and-drop it around the Kanban board.
Swim lanes are not supported on the FogBugz Kanban board, but that is also not available on Trello.
Since cases are the basic building blocks of FogBugz, we cannot avoid creating them, but we do not force you to add any details that you do not want to.
Adding a card
With your Kanban board opened, just click on the "+" sign in any of your columns, add a card title, and hit Enter. Your card is added. FogBugz will not require you to add any further details if you do not want to.
Repeat until you have all cards added.
Drag-And-Drop
Just drag-and-drop your cards to any of your Kanban columns, or move them around the current column.
Colors
We don't have card colors anymore.
But we have case type and case priority to use for categorizing your cards (cases). You can customize case types and priorities to your liking or to your own individual categorization requirements. Just be aware that these customizations will apply and show up within your whole FogBugz (for other users, too).
Assign the Cards
By default cards (cases) are assigned to the person who created them.
Just click on the name and select a different assignee from the drop-down list. Once selected the new assignee is automatically saved.
Organizing your Work
Pro Tip: The Iteration Planner works the same way as the Kanban board, except your columns are the Milestones.
If the corner store for your users is that they don't want to add any case details (except the title) and thus they don't want their cases to show up within the rest of the FogBugz (because maybe some other colleagues use FogBugz for case management), you could create your "Trello" Kanban board within a dedicated Milestone of a dedicated Project to which you can restrict the users that have access.