Well, there was the DDOS attack a few months back that greatly slowed down all transactions that were normally very quick. From what I understand it had to do with someone exploiting Nano's lack of fees and flooded the network with a ton of transactions, each only being worth a few cents. Someone correct me if I'm wrong, I'm admittedly a bit fuzzy on the details. I think it's since been fixed by patching the network nodes.
Right now, though? This is purely subjective, but I think the selection of wallets is still not great. I mean, sure, there's a bunch available and Nault gets recommended a lot, but it looks like it's an Electron app, which I am not a fan of. Still, it's better than wallets like Atomic, Exodus, Vola and WeNano, which don't have the source available. The situation with Android wallets kinda sucks, too. We do have them, but they all depend on Google's services. And, consequently, none of them are on F-Droid.
That said, I can't think of anything fundamentally wrong with Nano. The wallet situation might not be great, but it's nothing that can't be fixed.