I personally feel that until Linux gets dedicated (closed) sound drivers your results will be hit and miss with ALSA drivers. I think we needed dedicated low latency drivers like RME have made for Linux platforms; again you are still developing for two different style of distributions ... Redhat and Debian variants.
Creative did have some Linux beta drivers for the E-MU range although nothing ever came to fruition really AFAIK.
Another problem I would have is, direct hardware support for DSP, Dongle-based licenses and as Anderton mentioned cross-platform coding issues. Perhaps this could be resolved by using a wrapper to convert from Mac or Windows native code.
Then again, what did I knew?