Herpstat also makes a nice controller for humidity levels that isnt to expensive, but if I had to I would rather use a waterfall than a mister for previous reasons stated about the water density and RI chances. Bubbling / moving water would would cause a jump in humidity faster than standing water and would turn it on only when needed. With a timer I would be afraid that only a few minutes would be to much, or not near enough...with the Herpstat it would kick on and off only when needed keeping a fairly constant level.
I havnt used the Herpstat so I cant say how well it works, but I do plan on getting one.

Just my