I won't pass too much judgement on these until I try them or see other people try them, but I'm skeptical. I don't understand what advantages these would have over a butt connector. If anything, I would think crimping on a butt connector would be even quicker and offer a better physical and electrical connection, all for less money.
Edit: Huh, I guess I've just never heard of these and they're available
elsewhere under a few different names, including in different sizes. Some market them as waterproof and for marine or automotive applications. Neat.