Indeed, it's inevitable that there is some lag in operating sliders and other such interfaces via cloud-based services. It's completely out of our control that the optimal experience via a plugin will no longer be possible -- browser developers are simply taking that option away across the board, though we expect support to hold out through this year at the 32-bit level in the browsers we continue to list on the player download and CDF sites.
There are some possible bugs causing jumpiness you might be seeing in current slider behavior on the cloud, but my understanding is that will pass in one of the coming cloud updates (which happen on a fairly regular bi-weekly basis). One of the advantages of web-based services is the potential to correct discrete problems faster than through desktop software release cycles...
