Microsoft Research just released a video showing the lag on capacitive touch screens. I noticed the same when I bought my ASUS Transformer Prime last month. Tablets today have about a 100ms delay which you can notice if draw a swirly line at a fast speed. This can be annoying if you are trying to do drawings with some precision. Microsoft highlighted the difference when the lag was lowered to 50ms, 10ms and 1ms! I think this is the right direction to focus on before companies continue working on throwing tens of cores on a small processor.