Hello, an interesting change was done in beta-1-2-build-1, as it's written in the change-log : "Observer blocks no longer pulse twice when observing a retracting piston".

But, the result can be random and inconsistent, for example with the redstone build pic, the result is a kind of "random clock" stopping after 1 pulse or 3 or 5, etc... it's very unpredictable.

If you want more details about this inconsistent observer, I've done 2 minutes of video (and sorry for my french accent) here .