I get that same thing happening when browsing creative tabs sometimes, except it only lags for a few seconds. Turning off NEI fixes it for me. NEI seems to have game-breaking performance issues in 1.7.10. With it enabled, I lag for up to several seconds every time I open an inventory.
On another note, I got to thinking about 1.8 and how it seems to batch up several block updates into a single render chunk update. Its most notable when I'm breaking massive amounts of tall grass or instant-mining stone/dirt/sand. I'll see ghost blocks hang around for a very short time, then they all disappear at once in a single update. During the whole process, my FPS barely even fluctuates (<10fps decrease from 100+). That happens in pure vanilla 1.8, no mods other than MCPatcher's enhanced texturepack stuff. I even use a heavily modified version of the John Smith Legacy pack and a vanilla bloom shader on 1.8 with zero lag and fps issues.
1.7.10 seems to be the exact opposite. Causing even a single block update somewhere near where I'm at causes a 1-3 frame hiccup, per block that changes. Even running around breaking tall grass causes the game to turn into a slideshow until I stop. This happens regardless of whether I'm in vanilla or modded, or have Optifine and/or Fastcraft or not. Having just Fastcraft does nothing, adding Optifine slightly reduces the freezing. If the block updates happen near the edge of the view distance when I have Fastcraft installed, they barely affect my FPS and seem to get batched up into a single update just like 1.8 does. I noticed that after building a treefarm in Material Energy^4 using a lumber axe and autonomous activator. That pack has fast leaf decay enabled, so all the leaves on trees decay within roughly 1-2 seconds max (lots of spammed block updates and lag hell when I'm anywhere near it). I don't use a full texture pack in modded, only a modified water and lava texture and a couple other minor edits, which are all in the original vanilla resolutions.
I was reading the first post here and noticed this:
Quote from Player- Build performance intense structures (farms, effect heavy or dynamically rendered blocks etc.) further away. Chunks next to the player are the most expensive, they don't have their render cache updates throttled and the game won't try to cull costly geometry. Moving structures completely out of the view distance is even better.
I am now curious as to whether throttling updates at all distances like 1.8 seems to do would help reduce the stuttering when breaking blocks? I'd be more than willing to deal with broken blocks "ghosting" for a split second under high-load situations if it could mean a massive performance increase.