I installed misters in my greenhouse and have had great success using them to keep humidity up and perform evaporative cooling.
I would recommend installing a series of filters in your line (esp. calcium filter) to reduce mineral deposits on your leaves and in the lines.
My problem is that they are currently cycled on when my fans cycle on, ~85-90F, which can be a lot of on time when the outside air is 80F+. Even the little fog that is hitting the leaves builds up and everything ends up thoroughly saturated by the end of the day.
An aside:
Soon I'm going to design and build a custom greenhouse controller which will be <$200 for materials but should outperform many of the several hundred dollar ones, I'll open source the code for the microcontroller when I'm done.
Its going to incorporate solar energy harvesting for indefinitely powering the system which gives the bonus of detailed light intensity information. I'm going to add in a thermocouple, hygrometer, soil moisture detection and an 'electronic leaf'. With these inputs I should be able to switch on my foggers exactly when I need them. The system is also wireless based (I'm cobbling together several kits I had laying around) and I will incorporate remote data logging so that growers can monitor conditions without being on site.
Its going to be total overkill for the small greenhouse I have but should be a fun side project.
