I’ve found a little problem using yafray along with Blender and Yable tonight.
Some meshes I’ve made, very simple ones in fact (a plane extrude very few times, and duplicated with Alt-D several times) gave me very weird results, they scaled or streched insanely.
Is there a way to fix that? Thanks in advance cause I’ve got NO IDEA where it comes from 
Are you using eeshlo’s version or the “official” yafray version? He added some nice features, and made a few changes in the lighting system (that I’m not so happy with). But I bet the problem has to do with floating point inaccuarcy in the object’s matrix. Try creating your plane in top view, then alt-d and see if there is any difference.
Well, ‘my’ version is the ‘official’ version, it is not some sort of ‘fork’ or patch. And what exactly are you not happy with? All the old features are still there, so you can still do things the old way if you want. I don’t think I made any weird changes to the lighting system. There are some bugs however, not all from my code though. The ones we know about have already been solved.
As for the yable problem, I couldn’t recreate it. Did you parent anything? Even so, it “shouldn’t” really cause problems.
I discovered that parented object have strange behavoir when exported by YaBle in Yafray. For example, in Blender I parented a plane to the camera; the exported plane didn’t render at all, since I reexported it after removed the parent to the camera.
Env
maybe you should try CTRL+A. that solves parenting problems in the game engine. [>]
The changes aren’t weird, just slightly different. For example, with a sunsky background everything seems to be more illuminated. In the image I emailed you, the bottom is rendered with the latest yaf version. Look at the front faces and the interior cavity’s front face (on the green object). They look like they are being illuminated by another light. This may actually be more accurate, but it just doesn’t look right to me.