Since 1.7.4 I'm experiencing choppy video even though my framerate stays between 40-60 FPS, sometimes dipping into the high 20s in certain areas of my worlds. However, even when my framerate is between 40-60 FPS the game feels choppy when it did not in 1.7.2.
There is plenty of free RAM and CPU power available and my graphics card is an AMD Radeon HD 6770M with 1GB VRAM which can handle StarCraft 2 on medium settings.
I'm using the default resource pack.