The problem Hashi solves

It provides true token to the user on the destination chain so that user don't have to unwrap their tokens. For now the stable coins are supported but later an aggregator like 0x could be used to swap and bridge between any assets multichain.

Challenges I ran into

The most challenging thing is to find liquidity on the testnets. I integrated 0x protocol in the begining but because of no liquidity on testnets I had to remove it from the architecture. I was able to test the working of hyperlane messaging because it don't have any dependency on testnet tokens. We just need to native coin to pay for the gas.