Yeah, dave franks comments are pretty spot on with the exception that kayaking is way cooler. both are very cool with the exception of playboaters,of course.
downside to rafting is that rafters tend to
get stuck with all the logistics, planning, extra work of loading,rigging,unloading, dealing with the group poop(as in groover), the hours of gear checking/sorting/cleaning before and after a trip, dealing with the permit proccess and having the required permit gear at the launch. Along with the slight pressure that if you screw one thing up/forget one thing then you've ruined allot of people's vacation or weekend. Rafters tend to be better at all this too. Probably all the years of experience dealing with it and initially seemingly complex permit proccesses that become routine over time.
However, it an awesome feeling pushing out into the current at some hectic put in, putting the oars in the water ,relaxing abit and then disappear around the bend for a week of river camping, great food /beverage, whitewater and good company. It's all very worthwhile,at that point.
I should add that it is true that rafts and the whole rafting experience tends to make chics horny too. The booze,the warm sun, good food and going down a river all cleopatra style seems to get them going abit.