Before anything I want to say this; I have played minecraft since 2011, this is the first time I've ever had a gaming experience with lag.
I have taken a break from minecraft, probably left around mid 1.6, came back to the new 1.8 and I just can't play under these conditions.
The lag: Every probably 3-4 seconds of moving or mining a block.. or spinning my camera I will get an aggressive screen freeze, following 2-5 seconds of stop and go screen freezes. It's unplayable in the current situation.
I've tried allocating more memory, I've tried reducing the chunk loading down to 1-3, I've tried pretty much anything I can think of, and none of it even remotely makes it better