I bought my oldest son the first master set of HS (Valkyrie edition or somesuch)...
He loved it. my middle son loves it, they have a good friend who loves it.
So, I bought a different master set (can't remember which one - other than it isn't the marvel one)... And last xmas they each got a couple of the expansions...
They love it. I tried it once or twice, but didn't really get into it... maybe because I was playing against kids...
They'll put together these super elaborate maps and go at it - using all their figures, and split them up - I don't think they bother counting points to make sure the sides are even... they also make up their own rules a bit I think... but that's what kids do.