Since we always plan to have at least one nice sit-down meal in EPCOT, the CP Dinner Package is a no brainer for us. I also like the 15% discount that has been included with the package in the past. (It's a 15% discount on most, but not all, merchandise purchases on the day of your Package). The price of the package hasn't been more than the cost of the meal for us, but so far, we've only elected to eat at the Tier III restaurants.
Even with the package, it's a good idea to get into line 30 minutes or so ahead of the show. That way you get to select your seat (within the reserved section). Disney does reserve some of the better seats for "VIPs". Those are for the choir directors and chaperones of the high school choirs that participate.
If you are going to the CP on a weeknight early in December, you will not need a package (or have to stand forever in a line) to get a seat. However, to get a seat on the weekends or on the days closer to Christmas, you will either need to purchase the package or plan to spend a very long time in line - as much as 2 hours or more. Even then, you may not get in.
If seeing the CP is a priority for you, my advice is to splurge on a dinner package.