I found My Heritage to be absolutely awful - their "Smart Matches" are often only woefully vague approximations, much worse than those from Ancestry and Genes Reunited. I can't speak for their records or DNA but my impression is of an American bias, so it depends where your research is.
One of the most dispiriting features is that you can create a small tree there for free, but once it gets too big and/or too long after you joined, you can't access it without joining and more importantly, can't respond to people who have matching relatives. They say "please be kind and respond" when they really mean "please rejoin at the higher rate because you have a larger tree". At least when you don't resubscribe at Ancestry you can still exchange messages. I've resorted to trying to find people via Facebook, which has worked a couple of times.
To those who say "why not rejoin" well I can't afford to join all these sites, and my priority will be those that are more useful. I plan to rejoin FindMyPast next year for the 1921 census, obviously.
Other sites have the nous to realise that penalising people with larger trees so that they don't rejoin is counterproductive - accessible trees and free messaging opens up more potential and reachable relatives for new members (OK some junk, but better than nothing).
I'm not complaining so much for me, but for those often new My Heritage members who won't understand why I'm not replying to their messages. I always reply to a message where I can -and I never use GR's lazy "Sorry not my relative" option, but try to give an explanation.
