These look awesome - great hunting :)
If you take a look at their website, there are many options for over-shoes, and/or different set-ups - it's not just a one-Paleos-fits all. They are a little pricey, but I'd be tempted to say they're worth it if they do what it appears they do.
For anyone who's into beach, or water sports, especially where they're in and out of the [shallow] water, these are amazing. Think surfers, kite-boarding, wind-surfers, kayaks, anything water-based, whether ocean or river/lake.
When you're having to tread on your board/equipment, you need the grip. Then, when you're treading on sand, stone, rocks (and who knows what else), you need the protection. And these Paleos appear to be the perfect balance.
Even for those who like to walk bare-foot, but can't because they fear standing on something. These allow you the feeling (or close to it) of being barefoot, but the protection against whatever you might stand on - apparently even glass, or sharp stone/wood.
Amazing, amazing product. I'd love a pair - I have no idea which configuration though, as there are so many options.