In producing dynamic maps for students/users I have found the time invested in user testing well worth it. I use a varient of think aloud protocol called hallway testing. I grab any 2 or 3 likely users for 20 minutes each and set them a sample task (its important to get them to do something rather than just comment). They explain what they are doing when they get stuck or find something confusing and I prompt them if they aren't saying anything. Its a great way to discover consistent issues users have with your maps, most major problems will pop up with 3 users.
I use software to record the screen (silverback) but just taking notes was pretty effective. With a big project I also advocate 'test early, test often'.
I've found clients to be unhappy about funding user testing but its so quick and low tech that I tend to do it anyway to make sure there aren't unknown issues with a project
Do you use user testing when producing dynamic maps?
If so, what techniques have you found to be effective and why?