It depends. If you aren't interested in having dozens and dozens of photos, if you have a camera of your own and don't mind asking CMs/photogs to use it to take pictures of you -- AND if you don't mind "missing out" on ride photos (which are nice, but never clear enough that you'd want to print them and display them on the mantle at home), then MemoryMaker may not be a great investment.
We did it once and were disappointed with the quality of the photos and with the fact that there were too few photographers and too many lines to get to them. Plus, not all of our on-ride photos came out (flashes not in synch with on-ride cameras) and those that did weren't very clear. (Another advertised feature of MemoryMaker -- the Photoshopped "Magic Photos" -- were nothing we were interested in -- just a matter of personal taste.) Now we don't bother with MemoryMaker, stick with our own camera instead, and use the $150+ we'd have spent on it toward a table service meal. We still end up with enough lovely photos to make a vacation memory book when we get home -- we just don't have to pay for them.