CUSE is certainly a good thing. But it won't solve our problems entirely. OSS allows clients to read the playback pointer of the hw which apps use for synchronization. Now, in sound servers (and even on stuff like USB) we have a hard time to support this, since we usually have an extra latency "behind" the playback buffer. So, either the timing the application gets will be way off what actually is true -- or we will have to minimize that aforementioned extra latency at the cost of high CPU load.
So again. Regardless which approach we use: 100% compat won't happen.
LD_PRELOAD is good for some things, CUSE for others. But in the end, 100% OSS compat that works for everyone and always will stay a dream.