Weight paint not showing in viewport

I having problems to see weight effect area in the viewport.

For example in this file: http://bit.ly/1KYzGwKused in this tutorial https://www.youtube.com/watch?v=rkT92aoMpP0

Compare how its shown in the video (around 5:23) and this

In another test if I pose the object

And then try to weight paint on it

So obviously the weights are being applied to the object, I just can’t see it like its supposed to do.
Any ideas?

Seems to be a bug introduced in 2.73, up to 2.72 version it works, reporting to developers