There's too much fragmentation within the JAX NN library space, which penzai isn't helping with. I wish everyone using JAX could agree on a single set of libraries for NN, optimization, and data loading.
PyTorch code can't be called, meaning a lot of reimplementation in JAX is needed when extending and iterating on prior works, which is the case for most of research. Custom CUDA kernels are a bit fiddly too, I haven't been able to bring Gaussian Splatting to JAX yet.