I've just upgraded to 3.99.4b and now experience very annoying CPU hogging when using xmms, beep-media-player or audacious with crossfade plugin. Most of the CPU load is printed as system in top(1) output.
Unfortunately, I can't remember exactly what version I had been using before the upgrade. If you care to provide me with older versions, I'll find out when the bug was introduced. I think that the last time I upgraded was months ago.