I made an old project ("snow physics") that did not get a lot of attention, I think it is because I uploaded a map instead of writing everything so you don't have to download a snow physics map that looks so small and useless.

When Mojang just released the first snapshot with snow slabs I started messing around with it and discovered some very useful things. All of the things I have discovered are useful for making adventure maps, and few things are also useful for decoration and traps.

So, here are the facts:

1. Snow slabs stacked to a full block are a actually lower than a full block - exactly as low as soul sand.

2. Snow slab, if not stacked, not adds height to a normal block but does it to soul sand and makes it as high as a normal full block. (It also removes the slowness effect)

3. Snow slab is removed by flowing water water, any water flowing into the snow slabs block will just replace it.
This can be used to make a painting or write something on the floor that will be visible only when you put water on the floor. I used this trick in my undone adventure map.

4. Snow slabs block, unlike normal snow block, lets light to go through it. This is useful for hidden lighting.

5. When you stand on a snow slabs block you can place a block inside your legs.
If you want to suicide and you have shovel with you in a snow biome you can put two snow slabs under you, build two blocks height wall around you, jump, place a not transparent solid block under you, wait while you are suffocating in a wall.
This happens because you place the blocks inside your legs while you are in the air but you have where to fall and can't move to the sides so you fall one block down and the block you placed is now inside your head.

6. When snow slabs block gets pushed by piston it immediately disappears, same happens when you break the block under the snow slabs block.
This makes a massive blocks disappearing possible, you can make pistons to move the blocks under a huge snow slabs wall and the whole wall will immediately disappear. You also can to make the floor disappear by making a sand/gravel structure that falls when one block in the bottom is removed and put snow slab blocks above the sand.

7. You can't place torches, redstone dust, etc. on snow slabs block because it counts transparent block even when it's like a full snow block.

8. Snow blocks are unbreakable without shovel in adventure mode, but snow slab blocks can be destroyed easily.