We were at WDW in January and I also prepurchased the Photopass CD. It was great to come home and apply all of the graphics and then order the CD. Now that I have the CD I am doing an online scrapbook through Shutterfly.
There are pros/cons to either .... here are my thoughts...
Photopass Book:
Pros ..... adorable backgrounds, very Disney
Cons .... more expensive, limited to 4 photos/page, no spaces to journal or even caption photos.
Shutterfly or Snapfish:
Pros ...... better prices, often run sales, myriad of choices for layout designs, more photos per page offered as well as spaces to journal or place captions.
Cons ..... backgrounds are colorful and nice, but not specific Disney (but if you have PP photos, you can still have Disney graphics in your photos)
With the PP CD, you have the ability to use both PP and personal photos in any of the above mentioned photo books. For us, I like to get as many memories into each book as possible, so I like being able to place several photos on a page. Even so, most of my books end up being around 40 pages long!
I've used both Snapfish and Shutterfly. They are very similar. Shutterfly does offer a bit more in the line of layout choices, but Snapfish has better tools for modifying photos and better sales. After having used Snapfish for 3 books, it has been nice to try something different .... though I likely will go back to Snapfish after this book is done.
Hope that helps! I have amassed quite a collection of scrapping supplies, but have found that with online scrapping may just be the best way for me to actually accomplish something.