I hopped off the fence and took the plunge last night after posting here.
I did as much reading about them last night as I could and from everything I could read, they only affect POI not actual group size, which is what I've been reading about up till now as well. It sounds like the POI with the Magnetospeed attached typically raises POI anywhere from 1-3inches but group size is unaffected.
Should have one in a week or so and will hopefully have time to play with it before we leave for Banff for ski racing camp. Not for me, I'm to old and fat, but for my daughter.