Wow! Thanks everyone for the information. I conclude that RO will probably make a difference for me but perhaps not huge. Time to conduct an experiment methinks.
One thing about water that years of research taught us is that chlorinasted "city" water seems just fine for about a year, then your plants begin to decline and many can't be saved. Please do NOT use chlorinated water on orchids.
I found the same thing in reverse. After years of chlorinated city water, adding anti-chlor meant for aquariums and then switching to RO water I have seen remarkable growth just as Ray says as well. I do add fertilizer every watering though.