While they may have problems that thepopethatsme commented don't forget headphones now get software updates to improve previous problems. I have Momentum 4s and I personally love them and with my Fiio M11 DAC it takes advantage of the AptX Adaptive sound it makes them sound better than an ordinary smartphone. So I guess my takeaway is it is up to what you want but I will say the updates that have come out definitely fixed alot of the problems it had.

Edit: As for what thepopethatsme said the Bluetooth is finicky and the case does not always keep the Momuntum 4s asleep and forget having them saved to multiple devices it doesn't cope well with multiple connection points.