You can make arguments pro and con all day long, but in the end it comes down to what you prefer to use for certain exercises. There are benefits to both, and I think KB's are benefical for certain exercises. If you don't, that's cool. I've been working out continuously for about 35 years now, and I constantly change up what I am doing. Also, you really don't have to buy a bunch of KB's. I've got exactly 4---a 26 lb'r that my wife uses, and a 35, 44, and 53. That's it, a grand total of 4. I can do anything I need to with those 4, though I would like to get one heavier one at some point. I bought mine off ebay fairly inexpensively (except for shipping). I also have a complete Olympic weight set, 2 benches, Barbells, Dumbells, Pull-up/Dip bar, wavemaster and BOB bags, Hoist 210 machine, elliptical trainer, medicine balls, kicking shields and focus mitts, gloves, training knives.........and on and on. I've been collecting equipment for years, and add to it as I see fit. It is a lifetime endeavor like my training, so why limit myself?
As far as the "flipping" goes, I like it. It has added a lot of strength to my grip and forearms that I did not get with traditional weights, and after using them for over a year, I still get benefit from it. It has not caused my training to stagnate yet. Sure, you can do additional exercises with DB's to get a similar effect, but I like to keep my workouts to 30-35 minutes, combining weight-lifting, bodyweight exercises and cardio all in one intense circuit. KB's help me to keep the heart rate high, especially when doing high rep snatches and swings. YMMV.