(Windows and Mac only for now, Linux builds may not be too far behind)
I find this an exciting build to say the least, due to these three major things.
For a long time users who wanted very high GI quality without artifacts such as splotches had to contend with slow methods such as the path-based methods, which would make for a really slow render especially if you had glass objects. Thanks to the relentless work on improving and polishing the new SPPM (stochastic progressive photon mapping) implementation, the frustration of waiting days to weeks for a complex image to clear up is soon to be left behind. Thanks to this new feature, Luxrender 0.9 can render out scenes with highly complex materials like glass in a much shorter timeframe than Bidirectional path tracing or regular path tracing.
If you still need to use a path-based method, but need it fast, Hybrid mode now has support for GPU-based bi-directional path-tracing, allowing significant improvements to the quality you get when using the GPU (and Lux uses OpenCL so ATI users can use it too).
The final thing that some people might find to be a critical thing, is the initial support for normal mapping, now Luxrender will properly render your normal maps created either from a generator or from baking off of a sculpted model. There still is a few issues for some cases, but it seems for other cases they are already usable.
The latest Luxblend25 can be easily obtained from the mercurial repository and the newest revisions should work in 2.58, this also being a release that may keep you busy rendering things out until a bit more polish makes it way into the new Cycles engine, so download and enjoy.