If they can create or be par with Monero's privacy through that mixer, that can be one big thing for Ethereum. Well, that's an 'if'.
Good to know. With a mixer running on smart contracts, many ERC-20 tokens can be anonymized in a decentralized fashion. The only issue is that bugs and vulnerabilities on the mixer contract could greatly undermine the ETH blockchain if it's too complex. Remember, the greater the complexity of a smart contract, the greater the risks will be. I'd imagine that governments will be on mixer developer's tail in order to prevent people from using such services. The mixer contract will still be decentralized, but not many people will be able to use it if governments declare it to be "illegal".
At least, we know it's possible to create a mixer right on the ETH blockchain. With zkSNARKs and sidechains, mixers based on smart contracts could eventually replace centralized mixing services. It all depends on how people adopt decentralized mixers for their own privacy. If there's low demand, the idea of a mixer built on ETH smart contracts won't be going anywhere. I hope that talented developers make this possible in the future. Just my opinion