Direct quote from person managing the lines at the 9/11 Memorial Museum Tour:
"CityPASS is worthless during busy times of the year".
The reason this is the case is that you have to wait in CityPASS lines to get your tickets (exception is Empire State Building). Then you wait in line or visit attraction at scheduled time.
We visited Statue of Liberty. We spent 90 minutes in a CityPASS line to get tickets, then waited another 75 minutes on line to ferry. I say one poor couple who waited int the ferry line, then was informed they needed to get a ticket because CityPASS is not the ticket. Felt awful for them.
ANH was awesome, but I got there at 8:30 AM, 30 minutes before the museum opened. By 11:00 AM, the CityPASS line was brutal, but the entrance by the Space side was very short.
9/11 Memorial was the kicker. I arrived at 10 AM and was informed the CityPass line was 3 hours. I could have walked to the electronic ticket stations and bought a ticket with no line. To make this clear CityPass ADDED a minimum of 3 hours of waiting here!
You may save a few bucks with CityPass if you visit all of the attractions. But the trade off is that you will wait significantly longer in lines (especially during peak times like the holidays). In fact, I lost money using the CityPASS because I only had a 4 day trip and ended up not having the desire to spend an entire day waiting in lines.
Net is this:
1) Don't buy CityPASS.
2) Just go to the attractions you want to see, but go early. Right when they open.
3) CityPASS does not get you in advance or special lines. Rather you will be in longer lines. It did not save me time.
4) CityPASS may be OK if you plan to visit every single attraction during a time when you have no lines..
Enjoy New York!