Basically Block breaking/placing is slower the same with the sprint speed and you can really notice because the previous snapshot sprint and block placing was normal but now it is very noticeable
To reproduce all you need to do is
1.Sprint in 1.5.2 then in 13w21a you will see the diffrence
2.Place and break block in creative in 1.5.2 than in 13w21a
31st Duplicate of MC-16143, please use the search function to see if your bug has already been submitted. Currently over 56% of tickets are being closed as duplicate.