The performance of the charts in ExtJS 4.0 seems to be very low. For instance, in line charts there is a significant delay in drawing the points and animation even for 100 points or less.
I have seen mobile charting frameworks that are more responsive for such a reduced number of points.
Also, desktop charting packages become that unresponsive at 10000+ points.
I noticed the biggest slow down is happening in the (drawVerticalLabels and drawHorizontalLabels), it takes about 50% of the time to process the graphs. Also, in Sencha Touch these functions dont exist, they use something different for drawing labels.
I'm trying to optimize these functions a bit however so far I havent seen too much gain.