Nah. Touch screen cell phones are no more or less dangerous than any other cell phone. The danger comes from the magnetic field generated by the high frequency (usually PCS - which is in the microwave range) carrier, and you get that by holding the phone close to your ear while talking. But the relative size (not to mention the strength) of the field generated by the electronics needed for the touchscreen is minimal compared to the carrier frequency, so before you are talking on the phone (i.e. using the touch screen), there is no danger.
Ever hear about how policemen (and women) have a higher risk of throat cancer? That's because their radios are connected to their uniforms near their necks, and are thus susceptible to the high frequencies. So, to minimize the danger of the high frequency carrier while you are talking, always use an earpiece - or your speakerphone.
*** EDIT ***
There is no real difference between one cell phone and another, as far as the "danger" is concerned. And unless you are on your cell phone for most of the day, there is no real danger anyway. I only mentioned about the police because they wear their radios on their shoulders for at least eight hours every day, so they ARE at a greater risk, but if it were a huge risk, then you'd hear about that every day, and you don't. Just know that there is a risk, and, as with any risk, it's wise to take whatever precautions you can - such as by keeping some physical distance from your head while using the phone.
Again, it is minimal, but the "danger" from the high frequency carrier waves while the cell phone is in use is comparatively much greater than any threat posed by the touch screen itself.