Never seen any problems like that with LR 4.3, or any previous version either. One of LR's virtues has been it's stability over the years.
touching a large number of sliders before the effects of the first edit have rendered.
You're either working extremely fast or have a slow system. I only see LR rendering images when first loading and occasionally when playing with the colour temperature slider, most other things are keeping up with the speed I work now.
Win 7 64, i7 3770k, 32gb ram, SSDs, 3840x1440