I'm not the fastest (just sub-4 min) so take my impression for what it's worth.
So far, I'd consider my moyu to be an incremental improvement over my shengshou (which is spring swapped and lightly florian modded). The moyu is still a bit slow, but is improving daily in that regard. In particular, the outer layer turns don't match my shengshou's. Though the moyu should improve with more breaking in, I doubt it will make up the difference.
However, I prefer the moyu because of its stability. Accurate turning is still required but I can at least be more confident- particularly on the inner slices. Also, I can finally fingertrick double and triple slice moves, which I couldn't do on my shengshou because the layers wouldn't move together. I now have to retrain myself because I had changed my turning style to deal with this annoyance. I should also stress that I haven't put nearly as much work into the moyu than I've put into my shengshou. The same probably goes for everyone giving impressions in this thread. If you want something that will be passable with the least effort, go with the moyu, no question.
The moyu 6x6 is a bit of a letdown, but I think that's just due to overinflated expectations. Moyu's recent success makes us think they can do anything. Comparing a 6x6 to their recent 4x4 and 5x5 is just unfair. It's also unfair to compare a brand new cube to one that's been modded and broken in for years. I think with more time the reviews will improve. There's still no magic bullet when it comes to having a good 6x6, but I think the moyu is at least worth checking out.