The largest all-PureScript application I know of is SlamData[0], which takes about 12s for a rebuild, but SlamData uses a _lot_ of modules. For smaller projects it's much less. It's not great, but performance is one of three main goals for the current milestone. There is an alternative front-end called psc-compile[1] which reduces the incremental build times considerably. I hope to be able to integrate it soon.
