the taste description of manuka honey mentions an "earthy" taste. that may be why most of mine tend to end up a bit musky muddy tasting. its not a taste you notice when eating the honey but its a bit more noticeable when its watered down.
the health benefits of UMF grade manuka is well tested. its basically an anti bacterial. unfortunately it gets broken down in the intestines so eating it doesn't do a lot for you, tho it may help with ulcers. its main thing is for putting on cuts, burns etc. i think it still works against drug resistant bacteria. a few guys here do hospital grade and is sold to hospitals, army etc.
the labs can test for the active ingredient, MGO and also the precursor which converts into MGO.
one thing to watch is the cheaper table manuka is often kanuka. the plants look similar, honey taste is similar, the pollen is identical and in some areas of NZ they flower at the same time.
Rewarewa is really nice. i just don't get any locally but it is sold overseas so you guys should be able to get some.