I did something similar with genetic testing. It seemed to confirm what I already (somewhat) knew about which meds affected me in a certain way.

For example, I learned that I am a rapid metabolizer of drugs like Effexor (venlafaxine). So it taught me and my doctor that I need a pretty high dose of Effexor.

Anyway, as long as you are open to the possibility that it may not reveal anything riveting, but also the fact that it could open up new possibilities, then I'd say go for it.

Oh and also I don't know about how much it costs. I think my insurance at the time paid for it, but my current insurance definitely wouldn't pay for it (not the greatest insurance). Check and see if your insurance will pay for it, because they might.