I saw it today and downloaded the LR4 trial. Not sure it would be worth updating my LR3.6 if it didn't have RAW support for the Olympus EM5 and the Fuji. Very slow...... and I don't like not having the fill light.
I still don't have the XP1, but if I recall correctly, the JPG's were pretty darn good. On my X100, when using RAW, I have a hard time matching the JPG's from the camera. So maybe we shouldn't even bother shooting RAW in the XP1.
there's been no issue about "Fill light" ... however, Adobe have changed how you can handle light and shade in an image much more finely, so there are additional sliders (highlights, whites, shadows and blacks) ... "shadows" performs a somewhat similar (not identical) function to the old "Fill light" but the additional controls give you much greater fine-tuning.
However if you really want to use "fill light" as a single control, you can do so by setting your images to the "2010 process version" in Camera Calibration; however this also means you lose other improved controls such as the much better adjustment brush ; I also think denoise and sharpening is better in the 2012 PV.
I also dislike it when familiar interfaces change, but in this case I really do think it's for the better (I'll withhold judgement on performance until I've done a few more days with 4.1)
anyway, enough of taking this Fuji thread off at a tangent but hope it's been useful for BB + Christina