I've just pushed the 0.5.7 release of Ember. More information here.
This release includes a lot of new nifty authoring features, such as snap-to movement. We've also put some effort into getting it to run correctly (with all nice shader effects) on ATI cards. And there are lots of speedups, especially in the terrain handling code.
The multi-threading work done during this year's Google Summer of Code isn't included in this release because of a couple of regressions; it will hopefully be merged in soon though.