I'm glad to hear you were able to install the Intel graphics drivers. You may have a point with the stuttering, however, since I admit my system is also experiencing this and I haven't been able to isolate the cause since the graphics drivers were the first to be installed. The default Microsoft Display Adapter driver only offered a maximum resolution of 1024 x 768, so I couldn't live with that restriction. But my other laptop is running just fine in Windows TP Build 9860 and it's equipped with an NVidia GeForce 650M adapter, so this may indeed be the cause.
Intel will have to release an updated driver soon, or at least before the launch of the Consumer Preview, so we may have to live with the lagging until then. Unless someone who's technically inclined can find a workaround in the meantime.