Apple makes great devices, and I wouldn't use any other phone and tablet, but I think people like Gruber have been completely blind to the technological shortcomings of iOS devices in this area, because Steve Jobs told them styli are stupid, and the iPad is going to disrupt this-and-that.
It also brings up the whole "to stylus or not to stylus" discussion again, because one of the main reasons you wouldn't want to use a stylus for an iPad is that it highlights just how (comparatively) poor the touch latency is for the tasks that lend themselves to work with styli.
It perhaps best underscores that iPads are very much - still - disruptive technology, which by definition is in many ways inferior than sustaining technologies, but makes up for it in other compelling ways.
It's one of the many reminders that we shouldn't get too busy throwing out everything paper and analogue. Disruption is not synonymous with obviation.