"Is there sufficient evidence of beneficial effects of magnetic water treatment to warrant spending hundreds (sometimes thousands) of dollars on a magnetic treatment unit?"
We have done significant research on this controversial subject, and we believe it is unlikely that if you invest hundreds of dollars for a water conditioner that you would recoup your investment; as we have yet to see sufficient evidence that magnets, for residential use, really do much in most situations. It is certainly not worth spending many hundreds of dollars (in our opinion).

"Does magnetic water treatment perform as well as ion-exchange treatment?"
Definitely not. At present it is our opinion (after reading hundreds of magnetic reports and claims), that the conventional water softening technologies are much more reliable and also more effective.

"What do you base all of your negative feelings on regarding "magnetic conditioners"?"
Our opinion is based on non biased independent tests and studies by many people. One example is: The Consumer Reports a number of years ago in 1996 tested an over $500 magnet water treatment device. Two water heaters, over a two-year period, had over 10,000 gallons heated. One was "treated" with the magnetic treatment and one was not. The water heaters were cut open, and the tanks were found to contain the same quantity and texture of scale. There was no difference according to Consumers Reports.
That Consumer reports article saw no evidence that magnetic water conditioners work. Now many years later the latest "ours is different and better" magnetic conditioners are still not accepted as a good alternative to actual water softening.
We hope most of you will recognize to be VERY skeptical when some claim that THEIR water "conditioner" is "different" or "improved."
Buyer beware!

Note: Those who claim any product will solve all water problems used to be called a "snake oil salesman." You, the consumer, must do your homework ... and please: "buyer beware." We repeat ... we have NOT actually seen physical evidence, "proof," that any brand (no matter how expensive) of magnetic water "conditioner" actually works.