I actually put some on my iPad 2 and really like them so far.
I pre-ordered the iPad and Smart Cover when they went on sale online, but then got the iPad at Best Buy. I cancelled the online order for the iPad, but the Smart Cover had already shipped, so my iPad is naked until Tuesday.
I didn't like setting the bare aluminum back laying on a table, and I looked at my 13" MacBook Pro and said to myself, "Why doesn't the iPad have feet like this does?"
The wife says, "Why don't you try some of those clear rubber feet?" I had some in a drawer, put them on and it's been great. You don't notice that they're there and they keep the back from hitting the surface you set it down on. It also keeps it from sliding on the table.
We'll see what happens when the Smart Cover arrives, but so far, so good.