So on PBE Sylas has a lot of changes which have upset a majority of his player base. On the update for 12/16 he got the following change.
Petricite Burst (Passive) now notes "While Sylas has a charge of Petricite Burst, he gains 60% attack speed."
This was made to address the people who dislike how Riot has taken away his animation canceling/auto resetting mechanics. Take this information as you all will.