The coolest item seems to be a DS copy of Game & Watch Collection, which will run you 800 points (or coins, as they're being called). You can also get a deck of hanafuda cards for 800 points. From there on down, the rewards become a bit more superfluous, but still seem cool, with stuff like a Mario-themed game rack for DS carts, portable DS cart cases themed like Animal Crossing or Super Mario Bros., a DS Lite case, and a Wii Remote holder... which looks sort of like a tiny bag or something.
If you previously registered products via the old My Nintendo program, those products can be transferred over to your new Club Nintendo account. However, the website seems to be having some issues at the moment. It took me awhile to get my account transferred and set up for use, and then as soon as I tried to move one of my previously registered purchases over, it logged me out of the site and now refuses to recognize my password. That sounds like launch pains and is probably due to the site being flooded with new users, so if you're encountering similar problems, you might want to wait off a bit and try again later.