I'm not a big fan of using virtual sticks on an iOS device but sometimes there is no alternative. It comes down to how much time the developers put into implementing the virtual stick - some games play better than others. Tilt control from the accelerometer can be good too by the way in combination with on-screen buttons for fire for example. Again, depends on how much time the developers put into getting it right.
i love both, i actually think that touch controls are as precise as physical controls, and with the gyro the fps games can be even more precise than on a console or even a PC.
It depends because some devs can make it work perfectly like modern combat 2. After seeing the icontrol pad thing on the front page, it looks very cool but 70 dollars is not worth it, I don't think the virtual sticks cause any real problems for me.