Quote from Collin1971
Because they were already working on the 1.5.2 version before 1.6.2 and they wanted to finish the 1.5.2 version, it took so long because they have been working on a new system for lighting (threaded, less lag spikes). They'll update to 1.6.2 soon though.
can't wait to use it! and the new lighting engine, im hoping it will increase my fps because im ussually at 24 and i get lots of lag spikes