I imagine the experience would be about as interesting as taking an elevator down a tall building. Maybe I am missing something, though?
I think the big problems are that you need a hefty magnet (which is inherently dangerous) and you can't really split up the magnets over the body (because that is INSANELY dangerous), so you experience that same thing that could be achieved via bungee cord/harness.
You would also need to limit (lateral) movement quite a bit, to get reliable braking...
A x-shaped magnet assembly strapped to the back could work, but you probably could not allow the tube being all that much bigger in diameter than that backpack...
edit: If you allow any fall configuration different from feet-first, the terminal velocity has to be pretty low to reliably not kill people, too. But you could make this work with a net, I think...
I think there would be a similar experience to a reduced-gravity aircraft ride.
Its not necessarily just the physics of falling down a tube slowly thats interesting.
Getting a little whimsical, what if you had an Alice in wonder land experience. Wrap the whole "ride" in strange and fun visual effects while you fall down the rabbit hole.
Or, have protrusions from the tube where you could jump down to different levels and climb up the sides.
But, I really don't know the limitations or whats possible.