Wedding Guest Book

Ok, so I can not decide if this is a good idea or not.  Well, I think it's a good idea, I just don't know if it's worth it for the money.  A, I don't know how many times we will actually pull this out to look at, and B, I'm not sure if we would really use this camera again after the wedding.  BUT, it would be a cool thing to have.

http://weddingshop.theknot.com/weddingwarehouse/ProductPage.aspx?scId=OnSaleKWS(KnotShop)&pId=P2706(KnotShop)&cId=OnSaleKWS(KnotShop)&cTypF=OS#toppage  

It is a new version of a Polaroid camera, so the pictures turn out instantly and then the guests can put their picture in the book along with well wishes or their names or something.  

If I do buy this package deal from theknot.com, then I will still have to purchase additional film packets seeing as how it only comes with 40 pictures.  

However, the photo album only has spots for 30 photos and up to 75 guests...or at least thats what it says in the description.  I'm sure that I could squeeze more pictures into the book than what it says.  

What do you think?  I need HELP to decide what to do.