in minecraft 1.7
moving, running, walking, jumping, flying, doesn't lag the client at all.
using fancy graphics, render distance : 10 chunks
smooth lighting : max
and not having any lag

but in the 1.8 pre-release1 or any of the latest snapshots
when moving and render chunks lags alot
even with the lowest graphics and 2 chunks of rendering
that happens

you can see that in the attachments