There was a whole discussion a while back about using cassette cogs for SS conversions. It basically concluded that it's a bad idea because those cogs are designed to make shifting easier, which means they sort of want to drop the chain and may not be totally safe. I would do it to see if I like the gear, but in the end I think I'd get a cog without all the shaped teeth and cut outs.

Maybe this isn't a problem on a frame with horizontal drop outs since you can keep the chain tight always. With vertical drop outs you'll need a tensioner, which means the chain won't be under constant tension and tight.