FYI: Atomic swaps between Ethereum, Erc20 tokens and Bitcoin-based coins have now be completed successfully on mainnet!
Support for Eth/Erc20 is soon going to be added to Komodo's BarterDex p2p exchange, after just ~2 months since concept, the first "Etomic" swap between Eth and a bitcoin-based coin (Doge) has been completed on mainnet.
BarterDex works with on-chain atomic swaps. Ethereum doesn't have the opcodes necessary, for this reason many projects that are working on atomic swaps with Ethereum have focused on simulating the missing parts with smart contracts.
Komodo team has instead found a clever workaround that has rapidly led to success, it's less prone to bugs and also a lot cheaper in gas cost than all other solutions.