I have to say I'm surprised with such claims. I'm using Mycelium for quite a long time now and never, ever had any issue. In fact it's one of the best wallets I have ever used.
I'm not claiming it's not true that some users might have had some issues but I think there must be some reasonable explanation for that.
Nothing to do with their actual wallet. Everything to do with their piece of shit 'crowdsale' which delivered nothing other than one meeting in Majorca for them. Kind of odd how largely forgotten it is as it was plenty of money.
https://bitcointalk.org/index.php?topic=1455394.0