I just bought some, and I plan to use them. I like the idea of being able to get in and out of a color or size quickly. I can tie a knot as well as the next guy, but to claim there's a major difference between tying on directly, and using a clip is just folly. Otherwise none of these companies would be adding a split ring (oval or round). The clip acts about like an oval split ring.
Also, mess up with a knot, catch it on the sharp part of the split ring once or twice, and watch a $10 crank bait go flying, and that clip ain't quite so uncool....
Every day above ground is a good day... A day on the water; even better.