Every time I have ever checked the Disney package vs. buying hotel and tix separately, I have found a lower rate buying separate. The reason is that buying the package they charge you the full ticket price you would pay at the gate. However, if you go online direct with Disney you can get a cheaper ticket rate than that by $30-50 per person. And if you go with Ares or Getaway you can get cheaper still (by another $5-10 a person).
Further, it is my understanding that hotel only reservations are easier to cancel or modify. The package reservations are more restrictive.
If you buy the package, you do get a few extras like Toontown Morning Madness, priority seating for certain shows like Aladdin, and a pin or lanyard. See
http://disneyland.disney.go.com/dis...s/detail?name=ResortPackage2010Page&year=2010