During integration of Waku, we faced a problem with downtime of the nodes. We were unable to debug and test our solution, because the nodes were down. The official documentation was not so good, as well as react-hooks from the sdk were hard to use and unintuitive. In some cases, the official hooks were blocking the app and use window in global context, that broke the Next.js SSR

During the implementation the smart contracts in Rust for Arbitrum Stylus we faced the issues, that constructors are not yet supported there, and it was hard to implement pattern like Ownable. There was issues that stylus doesn't support returning of structures from functions and abi json generation brokes on complex types.