In the prior snapshots, experience orbs were slightly translucent in rendering. This no longer appears to be the case.
I consider their translucency to be intentional since this is also how they rendered in beta 1.8 pre-release 1, upon initial implementation.
Stained glass, ice, slime block and other transparent block particles are not transparent anymore
Experience orbs turn white when being picked up
Experience orbs are translucent
Experience orbs are not translucent
Experience orbs do not render behind other experience orbs when viewed from certain angles