The study mentioned by simcha merely alleges the glans of circumcised men is as sensitive as that of uncircumcised men, however circumcised men miss out on the added extra sensation afforded by a foreskin.
The sorrells study linked by steve concludes
The glans of the circumcised penis is less sensitive to fine touch than the glans of the uncircumcised penis. The transitional region from the external to the internal prepuce is the most sensitive region of the uncircumcised penis and more sensitive than the most sensitive region of the circumcised penis. Circumcision ablates the most sensitive parts of the penis.
It amazes me that nobody has attempted to measure the true sensitivity of the foreskin.
Touching only one spot on the penis to measure sensitivity is like only showing a person the color black to see if they're color blind.
Obviously the only way to measure the true differences between a cut dick and intact one is through the act of sex. Something tells me that it's going to be a long time before that happens, in the US at least.