iPhone: Excellent, multi-touch is well combined with elegant GUI.
Dell Latitude XT: Multi-touch zooming and panning is supplied. But its multi-touch response is quite slow.
HP Touch Smart: Multi-touch zooming is supplied only for photo browsing. In addition, you have to use two hands to activate multi-touch zooming in/out. One-hand pinching is not supplied.
Stantum: Unlike above three products, it adopts resistive touch technology. Sensitivity is improved compared with its predecessor Lemur but still far from satisfaction.