my camera has dual xd/cf, and personally, i love it. but, for the reasons i love it, would work for any dual formats. have both slots loaded, and when one gets full, a couple of button presses, and the camera is saving to the other card. takes only a few seconds, where as changing a card takes much longer (relatively), depending on how prepared you are for the switch.
but, for an entry level dslr, i think supporting 2 different types is a good decision to help draw people in from their p&s cameras. even if media isn't expensive, people don't like having to discard perfectly good memory cards. or maybe that is just thrifty people like me
