Yes, once you buy the CD you can get as many prints as you want.
Along with your pictures on the CD(s) you will also receive a copyright agreement from Disney giving you the right to make copies of the photos for your personal use. You should print this out to show wherever you have your pictures printed, or you'll need to send it to a site if you do your processing online (Shutterfly, WM, etc.) What you can also do is, once you receive your CD(s) is burn copies for your family/friends. That's what I'm going to do with 2 families that went to WDW at the same time we did as well as our famliy/friends that we got pictures with at DLR. That way they can print their own pictures.
And yes, it is a great deal-especially if you are going to DLR. DLR cd is only $59.95 which is a great deal when you consider 1 5x7 is $12.95. You'll want to buy your CD online, not in the parks. The CD you purchase in the park will not include any added enhancements (except the "magical" ones added by the photographer direct).
So once you go to DLR, go the PP website (disneyphotopass.com) and upload your card(s) You can upload as many cards as you want. You can continue to add cards to your account as well. When you upload your pictures, it will show an expiration date 30 days from your upload date. That is the date your pictures expire. You'll have to order your CD (or anything else) by that date or those pictures will disappear. You'll want to make sure that you get all the cards from your group and enter them on only one account. That way you'll only need to order one CD. (Depending on how many picutres you end up with, you'll actually receive multiple CDs-the is no limit on how many pictures you have on one (or more) CDs. I expect that I'll get 10-20 CDs with my recent order.
Luckily for me, Disney offered a deal to give you 30 extra days to do your pictures. I was able to take advantage of that and got 2 months worth of pix on my CD.
The PP cards, themselves, don't expire. You can continue to use them until they (Disney) comes out with a new system, if they do. I used my PP card from last year, this year at WDW and it caused a small problem. I wasn't able to upload those picture since they belonged to another PP account, already set up (A CD share group I was in last year). Luckily, I contacted Guest Services and they were able to transfer my photos to my new account.
Hope this helps, if you have any more questions, either post here or send me a PM. I'll do my best to answer you.
I also have hints, experiences, etc. that I plan on posting once I get my CDs so I can post pictures with it. I'll put a link in my siggy once I do.
Here's one quick tip-upload your pix as soon as you can. During certain times of the year, Disney adds more enhancements to the site. When they add some, they take some away. When we first returned from WDW in Sept (9-12) there were a lot of Halloween frames. Then as they added more enhancements (Pixie Hollow, WDW F&W, etc.) they started taking off the Halloween ones. Now that they have 12 Christmas season frames there are only 2 Halloween frames, 1 Fall frame, and 1 Thanksgiving frame left. So if you just got back from a recent Halloween trip to WDW or DLR you'll now have less frames to choose from. I'm surprised they took the HW frames off so soon, it was less than 2 weeks ago. I would be nice if special event frames would stay on the site at least 30 days from it happening. Are you listening Disney? I've got other suggests too!