If I do this at Amazon:

Put one of the 50% off titles in my cart
Choose "Save for later"

Will I be able to buy it tomorrow for 50% off?

Can't really save for sure. I know when you just had on you WISH LIST it wouldn't be.

BUT, during last weeks little fiasco w/Amazon & their "floating" discounts, I had 2 items in my SAVE FOR LATER cart. When the prices reverted back to normal they were still the earlier discounted price and I was able to check out with those prices.

Not really sure tho.

I had one in my save for later and the price went up.

"Save For Later" will definitely NOT preserve the price. You must put in an actual order for the price to stay...

Now this is weird - I put in 4 of the 50% off DVDs from Sept 12th's sale into my "Save For Later" cart and now (Sept 13th ~10:30am CST) 2 of them still show a 50% discount and the other 2 show the normal 15% discount.

Carnival of Souls - Criterion Collection
List Price: 39.95
Our Price: 19.97
You Save: 19.98 (50%)

Romy and Michele's High School Reunion
List Price: 29.99
Our Price: 25.49
You Save: 4.50 (15%)

The Exorcist - Limited Edition Collector's Set
List Price: 79.98
Our Price: 39.99
You Save: 39.99 (50%)

Devil Girl From Mars
List Price: 24.99
Our Price: 21.24
You Save: 3.75 (15%)

"Save for later" worked fine for me. I just ordered Notting Hill and Jungle Book for 50% off. If I clicked the link for Notting Hill or Jungle Book and chose "Open in new Window" they both came up with their old prices. But I was able to Proceed to Checkout and place the order for yesterday's discount.